Electric-component mounting system

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates in general to a method of supplying a suction nozzle with electric components (including electronic components), and an electric-component mounting system arranged to mount the electric components on a circuit substrate such as a printed-wiring board, and more particularly to techniques for reducing a failure of the suction nozzle to hold the electric components by suction.

2. Discussion of Related Art

A suction nozzle is arranged to hold an electric component by suction under a reduced or negative pressure, and is used in an electric-component mounting system, for example. In the electric-component mounting system, the electric component is supplied from a component supply device, and is held by the suction nozzle, so that the electric component is mounted on a circuit substrate. The suction nozzle is arranged to receive the electric components from the component supply device, at a predetermined component receiving position, but may suffer from a sucking failure, that is, a failure to correctly hold the electric component by suction, such as a failure to receive the electric component.

The sucking failure takes place due to inadequate positioning of the electric component with respect to the suction nozzle upon sucking of the electric component by the suction nozzle, a positioning error of the component supply device and a positioning error of a component-holding head which holds the suction nozzle. An adequate sucking position of the electric component at which the electric component can be sucked by the suction nozzle with high stability changes with the specific shape and size of the electric component, and may deviate from the center position of the electric component. The inadequate positioning error of the electric component with respect to the suction nozzle may be caused when the component supply device and the suction nozzle are positioned relative to each other such that the electric component is always sucked at its central portion by the suction nozzle. The positioning errors of the component supply device and the component-holding head may be caused by manufacturing and assembling errors and local thermal expansion of the component supply device, the component-holding head and the related devices. In view of the above, it has been a conventional practice to determine the sucking position of the electric component depending upon the specific kind of the electric component, obtain the positioning errors of the component supply device and the component-holding head, and position the sucking surface of the suction nozzle and the component supply device relative to each other, on the basis of the determined sucking position and the obtained positioning errors, for thereby reducing the inadequate positioning of the electric component with respect to the suction nozzle.

However, the conventional practice still suffers from the sucking failure due to inadequate positioning of the electric component with respect to the sucking surface of the suction nozzle. Where the suction nozzle includes a suction pipe whose end face functions as the sucking surface, for example, a bending of the suction pipe causes a positional deviation of the sucking surface with respect to the electric component, resulting in the sucking failure, such as a failure to receive the electric component or inadequate holding of the electric component that cannot be corrected. Conventionally, bending of the suction pipe is detected to check whether the suction pipe if bent can be used for mounting the electric component, or whether the bent suction pipe should be replaced with a new one. This detection of the bending of the suction pipe is affected for the purpose of avoiding the use of the defective suction nozzle for mounting the electric component. However, the bending of the suction pipe is not conventionally taken into account when the electric component is sucked by the suction nozzle. This is one of the reasons for the sucking failure in the prior art.

SUMMARY OF THE INVENTION

The present invention was made in view of the problems encountered in the prior art described above. It is therefore an object of the present invention to reduce a failure of the suction nozzle to correctly hold the electric component by suction, in a method of transferring the electric component from the component supply device to the suction nozzle, and an electric-component mounting system arranged to mount the electric component on a substrate.

The above object may be achieved according to any one of the following modes of the present invention in the form of a method of supplying a suction nozzle with an electric component and an electric-component mounting system. Each of the following modes of the invention is numbered like the appended claims and depends from the other mode or modes, where appropriate, to indicate and clarify possible combinations of elements or technical features. It is to be understood that the present invention is not limited to the technical features or any combinations thereof which will be described for illustrative purpose only. It is to be further understood that a plurality of elements or features included in any one of the following modes of the invention are not necessarily provided all together, and that the invention may be embodied without some of the elements or features described with respect to the same mode.

(1) A method of controlling an operation in which electric components are transferred one after another from a component supply device to a suction nozzle which is held by a component-holding head rotatable about an axis of rotation thereof, such that the suction nozzle extends in an axial direction of the component-holding head, each of the electric components being held by the suction nozzle by suction on a sucking surface provided at a free end of the suction nozzle, the method comprising:

a relative-position obtaining step of obtaining a relative position between the sucking surface and the axis of rotation of the component-holding head;

a relative-movement step of effecting a relative movement between the component-holding head and the component supply device on the basis of the relative position obtained in the relative-position obtaining step, so as to minimize an error of relative positioning between the sucking surface and a predetermined sucking position of the electric component positioned at the component-supply portion; and

a component supply step of moving, after the relative movement between the component-holding head and the component supply device in the relative-movement step, the component-holding head and the component supply device toward each other, for transferring one of the electronic components from the component supply device to said suction nozzle.

In the absence of a positioning error of the sucking surface with respect to the axis of the component-holding head (hereinafter referred to simply as “head axis”), there is established a predetermined relative position between the predetermined sucking position of the electric component and the head axis, so that there is established a predetermined relative position between the sucking surface and the predetermined sucking position, when the electric component (typically, an electronic component) is transferred from the component-supply portion to the suction nozzle. In the presence of a positioning error of the sucking surface with respect to the head axis, on the other hand, there exists a positioning error between the sucking surface and the predetermined sucking position of the electric component positioned at the component-supply portion. This positioning error between the sucking surface and the predetermined sucking position corresponds to the positioning error between the sucking surface and the head axis. Where the angular position of the component-holding head in which the relative position between the sucking surface and the head axis is obtained is the same as the angular position in which the electric component is transferred from the component-supply portion to the suction nozzle, the relative positioning error between the sucking surface and the predetermined sucking position of the electric component when the electric component is transferred from the component-supply portion to the sucking surface can be obtained on the basis of the obtained relative position between the sucking surface and the head axis. Accordingly, the sucking failure of the suction nozzle can be reduced, by moving the component-holding head and the component-holding device relative to each other so as to minimize the relative positioning error between the sucking surface and the predetermined sucking position.

The method according to the above mode (1) of this invention is effective particularly where the suction nozzle includes a suction pipe which has the sucking surface at its free end and which may have some degree of bending. According to the present method, the component-holding head and the component supply device are positioned relative to each other so as to minimize the error of relative positioning between the sucking surface and the component-supply portion, even in the presence of a relative positioning error between the sucking surface and the head axis, which is caused by bending of the suction pipe. When the electric component is transferred from the component-supply portion to the suction nozzle, the amount and direction of the relative positioning error which may be caused by the bending of the suction pipe are obtained, and the component-holding head and the component supply device are positioned relative to each other on the basis of the obtained relative positioning error, so as to minimize this error. The present method is effective to prevent a sucking failure of the suction nozzle even where the electric component is relatively small and the suction pipe has some degree of bending and/or positioning error.

(2) A method according to the above mode (1), wherein the relative-position obtaining step, the relative-movement step and the component supply step are affected when the component-holding head is placed in a same angular position thereof.

(3) A method according to the above mode (1), wherein the relative-position obtaining step, the relative-movement step and the component supply step are affected when said component-holding head is placed in a predetermined angular position thereof.

(4) A method according to any one of the above modes (1)-(3), wherein the relative-position obtaining step comprises:

a first image-taking step of operating an image-taking device to take a first image of the sucking surface in an axial direction of the component-holding head toward the sucking surface;

a rotating step of rotating the component-holding head about the axis of rotation by a predetermined angle;

a second image-taking step of operating the image-taking device to take a second image of the sucking surface; and

an obtaining step of obtaining a position of the axis of rotation of the component-holding head on the basis of at least the first and second images of the sucking surface taken in the first and second image-taking steps, and obtaining the relative position between the sucking surface and the axis of rotation.

The first imaging angular position in which the first image of the sucking surface is taken in the first image-taking step and the second imaging angular position in which the second image of the sucking surface is taken in the second image-taking step may both be different from the predetermined angular position in which the electric component is transferred from the component-supply portion to the suction nozzle, or one of the first and second imaging angular positions may be the same as the predetermined angular position, as in a method according to the following mode (5). The position of the axis of rotation of the component-holding head may be obtained on the basis of at least one additional image of the sucking surface as well as the first and second images taken in the first and second image-taking steps.

The center points of the first and second images of the sucking surface taken at the first and second angular positions of the component-holding head lie on a circle having its center on the axis of rotation of the component-holding head. The position of the axis of rotation of the component-holding head is obtained by calculation on the basis of the center points of the first and second images of the sucking surface and the first and second imaging angular positions with respect to a predetermined angular zero position of the head, namely, angular differences of the first and second imaging angular positions with respect to the angular zero position.

Where one of the first and second imaging angular positions is the same as the predetermined angular position, the first or second image of the sucking surface is taken in the angular position of the component-holding head in which the electric component is transferred from the component-supply portion to the suction nozzle. In this case, the positioning error between the center point of the image of the sucking surface taken in the predetermined angular position of the head and the obtained position of the axis of rotation of the head does represent the positioning error between the center point of the sucking surface and the axis of rotation of the head placed in the predetermined angular position. Accordingly, the calculation to obtain the position of the axis of rotation of the head is simplified. Where the first and second imaging angular positions are both different from the predetermined angular position, the center point of the sucking surface when the component-holding head is placed in its predetermined angular position lies on the circle on which the center points of the first and second images of the sucking surface lie. Therefore, the center point of the sucking surface when the head is placed in the predetermined angular position can be calculated on the basis of the known first and second imaging angular positions and the predetermined angular position with respect to the angular zero position of the head, and the center points of the first and second images of the sucking surface. Thus, the relative position between the center point of the sucking surface in the predetermined angular position of the head and the axis of rotation of the head can be obtained. In this case, however, the required calculation is relatively complicated and time-consuming.

(5) A method according to the above mode (4), wherein one of the first and second images of the sucking surface is taken when the component-holding head is placed in a predetermined angular position thereof.

(6) A method according to any one of the above modes (1)-(5), wherein the relative-movement step comprises moving the component-holding head to a predetermined position along a circular arc, and moving the component-supply portion of the component supply device in a direction of tangency to the circular arc.

According to the above mode (6) of this invention, the positioning error between the sucking surface and the predetermined sucking position of the electric component positioned at the component-supply portion is substantially zeroed in the direction of movement of the component-supply portion, by moving the component-supply portion.

(7) A method according to any one of the above modes (1)-(6), wherein the electric component is transferred from the component-supply portion of the component supply device to the suction nozzle held by a selected one of a plurality of component-holding heads, and a relative movement between the selected component-holding head and the component supply device is affected in the relative-movement step, on the basis of a relative positioning error of the axes of rotation of the plurality of component-holding heads, as well as the relative position obtained in the relative-position obtaining step. For instance, the relative movement between the selected component-holding head and the component supply device is affected on the basis of a positioning error of the axis of rotation of the selected component-holding head with respect to the axis of ration of a reference component-holding head which is selected from the plurality of heads.

(8) A method according to any one of the above modes (1)-(7), wherein the relative movement between the component-holding head and the component supply device is affected in the relative-movement step, on the basis of a positional difference between the predetermined sucking position of the electric component and a center of the component-supply portion when the electric component is ready to be transferred from the component-supply portion to the suction nozzle, as well as the relative position obtained in the relative-position obtaining step.

(9) An electric-component mounting system for mounting electric components on a circuit substrate, comprising:

a component supply device having a component-supply portion from which the electronic components are supplied one after another;

a circuit-substrate support device for supporting the circuit substrate;

a component-holding head rotatable about an axis of rotation thereof and arranged to removably hold a suction nozzle having a sucking surface such that the suction nozzle extends in an axial direction of the component-holding head;

a head rotating device operable to rotate the component-holding head;

a relative-movement device operable to move the component-holding head, the component supply device and the circuit-substrate support device relative to each other, in a direction intersecting the axis of rotation of the component-holding head;

an axial-movement device operable to move the component-holding head and the component supply device in the axial direction toward and away from each other;

an image-taking device operable to take an image of the sucking surface in the axial direction toward the sucking surface; and

a control device operable to control the head rotating device, the relative-movement device, the axial-movement device and the image-taking device,

and wherein the control device includes

a relative-position obtaining portion operable to obtain a relative position between the sucking surface and the axis of rotation of the component-holding head;

a relative-movement control portion operable to control the relative-movement device, for effecting a relative movement between the component-holding head and the component supply device on the basis of the relative position obtained by the relative-position obtaining portion, so as to minimize an error of relative positioning between the sucking surface and a predetermined sucking position of the electric component positioned at the component-supply portion; and

a component-transfer control portion operable after the relative movement between the component-holding head and the component supply device by the relative-movement device, to control the axial-movement device to move the component-holding head and the component supply device toward each other, for transferring one of the electric components from the component-supply portion of the component supply device to the suction nozzle.

An electric-component mounting system may use a plurality of component-holding heads which, for example, are mounted on a rotating body rotatable about its axis, such that the component-holding heads are equiangularly spaced from each other along a circle having its center on the axis of rotation of the rotating body. The rotating body may be an indexing disk which is intermittently rotatable about its axis, or a rotary body which is rotatable in opposite directions by predetermined angles. The intermittently rotatable indexing disk is intermittently rotated by a suitable rotary drive device so that the component-holding heads are turned about the axis of rotation of the indexing disk, and are sequentially stopped at a plurality of working positions arranged along a circular path of turning movement. The component supply device is located at one of the working positions, while the circuit-substrate support device is located at another working position. The rotary body which is rotatable in the opposite directions by the predetermined angles is also rotated by a suitable rotary drive device so that the component-holding heads are turned about the axis of rotation of the rotary body, and are stopped at predetermined working positions. In either of these cases, the rotating body and the rotary drive device constitute the head rotating device indicated above.

The component-holding heads may be supported by respective support members which are arranged about a common axis of turning such that the support members can be turned about the common axis of turning, independently of each other. When the support members are turned about the common axis by a suitable turning device, the support members are sequentially stopped at one or more working positions, at a predetermined time interval. The component-holding heads are supported by the respective rotatable members such that the heads are spaced by the same distance from the common axis of turning. In this case, the support members and the turning device constitute a head moving device in the form of a head turning device operable to turn each component-holding head along a circular path.

The electronic-component mounting system may use at least one component-holding head mounted on a movable member which is linearly movable in a plane, in at least one of two mutually perpendicular directions. Where the movable member is movable by a positioning device in the two mutually perpendicular directions, each component-holding head can be moved to a desired position in the above-indicated plane. In this case, the movable member and the positioning device constitute a head moving device operable to move each component-holding head. The relative-movement device indicated above includes this head moving device.

The above-indicated rotating body and rotary drive device or the above-indicated plurality of support members and turning device may be mounted on a movable member which is movable in a plane in two mutually perpendicular directions. The axis of rotation of the rotating body or the common axis of turning of the support members may be perpendicular to the surface of the circuit substrate supported by the circuit-substrate support device, for instance, parallel to the vertical direction, or may be inclined with respect to the vertical direction. In this case, the relative-movement device indicated above includes the rotating body, the rotary drive device, the movable member and a positioning device for moving the movable member, or the support members, the turning device, the movable member and the positioning device.

The circuit-substrate support device may be stationary, or movable by a suitable positioning device to move and position the circuit substrate. In the latter case, the relative-movement device indicated above includes the positioning device to move the circuit substrate together with the circuit-substrate support device.

The component supply device may be stationary, or movable by a suitable positioning device to move the component supply device. In the latter case, the relative-movement device indicated above includes the positioning device to move the component supply device.

The component supply device, which is stationary or movable, includes a plurality of feeders, and a support block or table on which the feeders are mounted such that the component-supply portions of the feeders are arranged in s straight low. Each feeder accommodates a plurality of electric components of the same kind. Each feeder may be a tape feeder having a tape cartridge arranged to feed a carrier tape accommodating electric components, such that the electric components are fed one after another to the component-supply portion of the feeder. Alternatively, the feeder is arranged to feed a succession of electric components by means of a vibrator, a slideway, an air stream or a conveyor belt, or a combination thereof, such that the electric components are fed one after another to the component-supply portion. In either of these cases, the feeder includes a storage device accommodating the electric components, and a feeding device for feeding the electric components from the storage device to the component-supply portion.

Where the component supply device is movable, the support block or table supporting the feeders is moved by a table positioning device in a direction parallel to the direction of arrangement of the component-supply portions, so that the component-supply portion of a selected one of the feeders is located at a predetermined component supply position. The component-supply portions of the feeders may be arranged along a straight line, or any other lines such as a circle, a circular arc or a curve (other than the circular arc), or a combination thereof. The feeding device and the storage device of the movable component supply device may be mounted on a common support block or table, so that the feeding deice and the storage device are moved together when the common support block is moved. Alternatively, the feeding device and the storage device may be mounted on separate support blocks, respectively. In this case, the feeding device and the storage device may be mounted on respective movable support blocks so that the feeding device and the storage device are movable independently of each other. Alternatively, the storage device may be stationary.

The component supply device may be of tray type having a plurality of trays each having a multiplicity of component-accommodating recesses accommodating the respective electric components.

The image-taking device is arranged to take the image of the sucking surface of the suction nozzle in the axial direction of the component-holding head toward the sucking surface. The image-taking device may be a CCD camera, which may be disposed concentrically with the component-holding head such that the CCD camera is opposed to the sucking surface of the suction nozzle. Alternatively, the CCD camera and the component-holding head may be juxtaposed in parallel relationship with each other such that the CCD camera faces downwards. Where the CCD camera is not opposed to the sucking surface, as in the latter case, a waveguide device is provided to guide a light indicative of the image of the object (sucking surface) so as to be incident upon the CCD camera. In this case, the waveguide and the CCD camera constitute the image-taking device.

The image-taking device may be a surface-imaging device arranged to take a two-dimensional image of the object at one time, or a line sensor which includes a multiplicity of image-taking elements arranged in a straight line. In the line sensor, a two-dimensional image is formed by multiple lines of image which are taken successively while the line of the image-taking elements is moved relative to the object.

The electric-component mounting system constructed according to the above mode (9) of this invention provides substantially the same effects and advantages as described above with respect to the method according to the above mode (1). The feature according to the above mode (4) or (5) is applicable to the electric-component mounting system according to the above mode (9).

(10) An electric-component mounting system according to the above mode (9), wherein the relative-position obtaining portion, the relative-movement control portion and the component-transfer control portions are all operable when said component-holding head is placed in a predetermined angular position.

(11) An electric-component mounting system according to the above mode (9) or (10), wherein the relative-movement device comprises:

a head turning device operable to turn the component-holding head about a turning axis, such that the component-holding head can be sequentially stopped at a plurality of working positions which are arranged along a circular path of turning of the component-holding head; and

a component-supply-device positioning device operable to move the component supply device in a direction of tangency to the circular path of turning, to bring the component-supply portion into alignment with one of the working positions.

(12) An electronic-component mounting system according to any one of the above modes (9)-(11), wherein the relative-movement control portion is operable to control the component-supply-device positioning moving device for positioning the component supply device such that the error of relative positioning between the sucking surface and the predetermined sucking position of the electric component in the above-indicated direction of tangency is substantially zeroed.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features, advantages and technical and industrial significance of the present invention will be better understood by reading the following detailed description of presently preferred embodiments of the invention, when considered in connection with the accompanying drawings, in which:

FIG. 1 is a plan view schematically showing an electronic-component mounting system constructed according to one embodiment of this invention;

FIG. 2 is a side elevational view (partly in cross section) of a component mounting device of the electronic-component mounting system of FIG. 1;

FIG. 3 is a plan view showing a covering member of a tape feeder of a component supply device of the electronic-component mounting system;

FIG. 4 is a view for explaining working stations of component-holding heads of the component mounting device of FIG. 2;

FIG. 5 is a front elevational view (partly in cross section) of an angular-head-position resetting device of the component mounting device;

FIG. 6 is a front elevational view (partly in cross section) showing a suction nozzle as held by a mounting head of the component mounting device;

FIG. 7 is a front elevational view (partly in cross section) showing an imaging system arranged to take an image of an electronic component held by the component mounting device;

FIG. 8 is a block diagram showing a part of a control device for controlling the electronic-component mounting system, which part largely relates to the present invention;

FIG. 9 is a view for explaining a sucking position of the suction nozzle at which the electronic component is held by suction by the suction nozzle when the electronic component is positioned at a component-supply portion of the tape feeder of the component supply device;

FIGS. 10A and 10B are views for explaining a manner of detecting the axis of rotation of the suction nozzle;

FIG. 11 is a view for explaining a manner of detecting a positioning error of the sucking surface of the suction nozzle;

FIGS. 12A and 12B are views for explaining manners of setting and adjusting positioning data of the tape feeder on the basis of the positioning error of the sucking surface;

FIG. 13 is a view for explaining a manner of detecting a positioning error of the tape feeder;

FIG. 14 is a view for explaining a manner of adjusting the positioning data of the tape feeder on the basis of the positioning error of the tape feeder as well as the positioning error of the sucking surface;

FIG. 15 is a plan view showing an electronic-component mounting system constructed according to another embodiment of this invention;

FIG. 16 is a side elevational view of the electronic-component mounting system of FIG. 15;

FIG. 17 is a front elevational view (partly in cross section) of the electronic-component mounting system of FIG. 15;

FIG. 18 is a side elevational view (partly in cross section) of a component mounting device of the electronic-component mounting system of FIG. 16; and

FIG. 19 is a block diagram showing a part of a control device for controlling the electronic-component mounting system of FIG. 15, which part largely relates to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring first to FIG. 1, reference numeral <b>10</b> denotes a machine base of an electric-component mounting system in the form of an electronic-component mounting system <b>12</b>. The electronic-component mounting device <b>12</b> includes a component supply device <b>14</b>, an component mounting device <b>16</b>, and a circuit-substrate support device in the form of a printed-wiring board supply device (hereinafter abbreviated as “PWB support device”) <b>18</b>, which are mounted on the machine base. <b>10</b>.

The component supply device <b>14</b> includes two component supply tables <b>30</b>, <b>32</b>. However, only one of these two component supply tables <b>30</b>, <b>32</b> may be provided. Each of the two component supply tables <b>30</b>, <b>32</b> includes a feeder support block <b>34</b>, and a plurality of tape feeders <b>36</b> mounted on the feeder support block <b>34</b>. Each tape feeder <b>36</b> is arranged to feed a carrier tape <b>22</b> (FIG. 2) which accommodates electric components in the form of electronic components <b>38</b> (FIG. <b>6</b>).

The carrier tape <b>22</b> includes a carrier substrate (not shown) which has a multiplicity of component-accommodating recesses formed at a suitable interval along the length of the tape. The electronic component <b>38</b> are accommodated in the respective component-accommodating recesses, and the opening of each recess is closed by a covering film bonded to the carrier substrate. The carrier tape <b>22</b> is fed on a body of the tape feeder <b>36</b>, and a front portion of the tape feeder <b>36</b> which is located on the side of the component mounting device <b>36</b> is covered by a covering member <b>24</b>, as shown in FIG. <b>2</b>. The covering member <b>24</b> is attached to the body of the tape feeder <b>36</b> such that the covering member <b>24</b> is movable between its closed and open positions in which the opening <b>26</b> is closed and open, respectively. As shown in FIG. 3, the covering member <b>24</b> has an opening <b>26</b> through which each electronic component <b>38</b> is taken out from the carrier tape <b>22</b>.

In operation of each tape feeder <b>36</b>, the carrier tape <b>22</b> is fed by a feeding device (not shown), with a predetermined pitch while the covering film is separated from the carrier substrate, at the covering member <b>24</b>. Thus, the electronic components <b>38</b> are fed one after another to a predetermined position at a component-supply portion <b>37</b> (FIG. 3) of the tape feeder <b>36</b>. The component-supply portion <b>37</b> has the opening <b>26</b> through which each electronic component <b>38</b> is taken out by the component mounting device <b>16</b>. The plurality of tape feeders <b>36</b> are removably mounted on the feeder support block <b>34</b> such that the component-supply portions <b>37</b> of the tape feeders <b>36</b> are arranged along a straight line, namely, along a horizontal straight line in the present embodiment. When the carrier tape <b>22</b> is advanced by the feeding device, the covering member <b>24</b> is moved with the carrier tape <b>22</b> such that the covering member <b>24</b> closes a half of the opening of the uncovered leading component-accommodating recess. When the electronic component <b>38</b> is picked up by a suction nozzle of the component mounting device <b>16</b>, only the covering member <b>24</b> is retracted to fully open the component-accommodating recess in which the electronic component <b>38</b> in question is accommodated. At this time, the electronic component <b>38</b> can be picked up by the suction nozzle through the opening <b>26</b>. In this condition, the component-supply portion <b>37</b> is operable to permit the electronic component <b>38</b> to be picked up through the opening <b>26</b>.

In the electronic-component mounting system <b>12</b> of the present embodiment, movement data for positioning and moving the component supply tables <b>30</b>, <b>32</b>, PWB support device <b>18</b> and other movable members are defined in an XY coordinate system having an X-axis direction and a Y-axis direction as indicated in FIGS. 1 and 4. That is, the X-axis and Y-axis directions of the XY coordinate system are respectively parallel to the horizontal and vertical directions as seen in the plan views of FIGS. 1 and 4 wherein the component supply device <b>14</b> is located above the PWB support device <b>18</b>. The upward and rightward directions in FIG. 4 are positive X-axis and Y-axis directions, respectively. The XY coordinate system of the electronic-component mounting system <b>12</b> as seen in the downward direction, as in the plan view of FIGS. 1 and 4, is convenient to define the movement data, since operations of the component mounting device <b>16</b> to pick up the electronic components <b>38</b> from the component supply device <b>14</b> and to mount the electronic component <b>38</b> on a printed-wiring board <b>60</b> are performed on and above the component supply device <b>14</b> and the printed-wiring board <b>60</b>. In the present embodiment, the component-supply portions <b>37</b> of the tape feeders <b>36</b> are arranged in the X-axis direction (in the right-and-left direction of FIG. <b>1</b>).

The feeder support block <b>34</b> of each component supply table <b>30</b>, <b>32</b> has a ballnut <b>39</b> fixed thereto. The ballnut <b>39</b> engages a feeds crew in the form of a ballscrew <b>40</b>, which is rotated by a support block drive motor <b>42</b>, so that each component supply table <b>30</b>, <b>32</b> is moved in the X-axis direction while being guided by a guiding device including a guide rail <b>44</b>. Thus, the component-supply portions <b>37</b> of the plurality of tape feeders <b>36</b> are selectively brought into a predetermined component supply position . The ballscrew <b>40</b> and the support block drive motor <b>42</b> constitute a major portion of a support-block positioning device or table positioning device <b>46</b> operable to move each component supply table <b>30</b>, <b>32</b>. In other words, the two component supply tables <b>30</b>, <b>32</b> are respectively moved by two table positioning devices <b>46</b>, which cooperate to provide a component-supply-device positioning device <b>48</b>. The guide rail <b>44</b> is used commonly for the two component supply tables <b>30</b>, <b>32</b>. The electronic components <b>38</b> are supplied from the two component supply tables <b>30</b>, <b>32</b> in a manner well known in the art, for instance, in a manner as disclosed in JP-B2-2-21719. In FIG. 1, the nut <b>39</b> of the component supply table <b>30</b> is shown, but the tape feeders <b>36</b> mounted on the table <b>30</b> are not shown, while the tape feeders <b>36</b> of the component supply table <b>32</b> are shown, but the nut <b>39</b> of the table <b>32</b> is not shown.

The PWB support device <b>18</b> is arranged to support or hold a circuit substrate in the form of the printed-wiring board <b>60</b>, and is moved by a circuit-substrate positioning device in the form of a board positioning device <b>64</b>, to a desired position in the above-indicated XY coordinate system defined by the mutually perpendicular X and Y axes. The board positioning device <b>64</b> includes an X-axis slide <b>74</b>, and a Y-axis slide <b>82</b> movably mounted on the X-axis slide <b>74</b>. The X-axis slide <b>74</b> is movable in the X-axis direction by an X-axis drive motor <b>68</b> through a feed screw in the form of a ballscrew <b>70</b> while being guided by guide rails <b>72</b>, while the Y-axis slide <b>82</b> is movable in the Y-axis direction by a Y-axis drive motor <b>76</b> and a feed screw in the form of a ballscrew <b>78</b> while being guided by a guide rails <b>80</b>. Thus, the board positioning device <b>64</b> serves as an XY positioning device.

The PWB support device <b>18</b> is mounted on the Y-axis slide <b>18</b>, and is arranged to support the printed-wiring board <b>60</b> such that the board <b>60</b> maintains a horizontal attitude or posture. The top surface or component-mounting surface of the printed-wiring board <b>60</b> has a plurality of component mounting positions at which the electronic components <b>38</b> are mounted by the component mounting device <b>16</b>. With the printed-wiring board <b>60</b> moved with the PWB support device <b>18</b>, the component mounting positions on the board <b>60</b> are sequentially brought into alignment with a predetermined component mounting position (described below) of the component mounting device <b>16</b>.

In the present embodiment, two fiducial marks <b>88</b> are provided on the top surface of the printed-wiring board <b>60</b>. An image-taking device in the form of a fiducial mark camera <b>90</b> (FIG. 1) is provided take images of the fiducial marks <b>90</b> on the printed-wiring board <b>60</b> held by the PWB support device <b>18</b>. The fiducial mark camera <b>90</b> is fixedly disposed by a frame (described below) of the component mounting device <b>16</b>, such that the fiducial mark camera <b>90</b> faces downwards to take the images of the fiducial marks <b>88</b> in the downward direction.

The fiducial mark camera <b>90</b> includes a matrix of solid image sensors in the form of CCDs (charge-coupled devices), and a lens system, and functions as an image-taking device in the form of a surface-imaging device capable of taking a two-dimensional image of an object at one time. The DDCs are small-sized light receiving elements arranged in a matrix in a plane. Each of the light receiving elements generates an electric signal depending upon an amount of light received. The matrix of the light receiving elements defines an imaging area in which an image of the object is formed. An illuminating device (not shown) is provided near the fiducial mark camera <b>90</b>, to illuminate the object and its vicinity when the image of the object is taken by the fiducial camera <b>90</b>.

Referring next to FIG. 2, the component mounting device <b>16</b> will be described only briefly since the component mounting device <b>16</b> per se does not significantly relate to the present invention. The component mounting device <b>16</b> in the present embodiment is similar in construction with a component mounting device as disclosed in JP-A-6-342998, and co-pending U.S. patent application Ser. No. 09/963,431 filed May 24, 2001 issued as U.S. Pat. No. 6,507,997 B2 on Jan. 21, 2003, claiming priority of Japanese Patent Application No. 2000-164958.

In FIG. 2, reference numeral <b>110</b> denotes a frame supported by the machine base <b>10</b>. The frame <b>110</b> supports a rotary shaft <b>112</b> such that the rotary shaft <b>112</b> is rotatable about a vertically extending axis. The rotary shaft <b>112</b> is rotated by a rotary drive device <b>114</b>, which includes a roller gear and a roller-gear cam (not shown). The roller-gear cam is rotated in one direction at a constant speed by an intermittent rotary drive motor <b>116</b> (FIG. <b>8</b>), so that a plurality of rollers of the roller gear are sequentially brought into engagement with a cam rib of the roller-gear cam, whereby the rotary shaft <b>112</b> is intermittently rotated by a predetermined angle about the vertical axis.

The rotary shaft <b>112</b> has a lower end portion extending downward from the frame <b>110</b>. To this lower end portion of the rotary shaft <b>112</b>, there is fixed a rotating body, more specifically, an intermittently rotating body in the form of an indexing disk <b>120</b>. The indexing disk <b>120</b> carries <b>16</b> component-holding heads <b>130</b> arranged equiangularly in its circumferential direction such that each component-holding head <b>130</b> is movable in the axial direction of the indexing disk <b>120</b>, that is, movable in the vertical direction, and such that each component-holding head <b>130</b> is rotatable about its axis. The component-holding heads <b>130</b> are provided to receive the electronic components <b>38</b> from the component supply device <b>14</b>, and mount the electronic components <b>38</b> on the printed-wiring board <b>60</b>.

When the rotary shaft <b>112</b> is continuously rotated, the indexing table <b>120</b> is intermittently rotated at an angular spacing interval of the 16 component-holding heads <b>130</b>, that is, at an angular interval of 22.5°. Thus, the 16 component-holding heads <b>130</b> can be turned about a vertically extending common turning axis, namely, about the axis of rotation of the indexing disk <b>120</b>, so that each component-holding head <b>130</b> can be temporarily stopped at 16 working stations or positions which are equiangularly spaced from each other along a circular path of movement. The 16 working positions include: a component receiving position <b>130</b>A at which each electronic component <b>38</b> is received or picked up by suction from a selected one of the tape feeders <b>36</b> of the component supply device <b>14</b> (at which the electric component <b>38</b> is transferred from the selected tape feeder <b>36</b> to a suction nozzle <b>190</b> described below); a component attitude changing position <b>130</b>C at which the attitude or angular position of the electronic component <b>38</b> is changed; a component hold-position detecting position at which the position of the electronic component <b>38</b> held by the component-holding head <b>130</b> is detected; a component hold-position rectifying position <b>130</b>E at which the angular position of the electronic component <b>38</b> is adjusted; a component mounting position <b>130</b>F at which the electronic component <b>38</b> is mounted on the printed-wiring board <b>60</b>; an angular-head-position resetting position <b>130</b>G at which the component-holding head <b>130</b> is rotated to its predetermined angular-zero position; a nozzle-holder detecting position <b>130</b>I at which a currently selected one of nozzle holders <b>190</b> (described below) is detected; and a nozzle-holder selecting position <b>130</b>J at which the nozzle holder <b>190</b> to be used next is selected. In the present embodiment, the rotary shaft <b>112</b> and the rotary drive device <b>114</b> constitute a major portion of an intermittently rotating device operable to intermittently rotate the indexing table <b>120</b>, and the intermittently rotating device and the indexing table <b>120</b> constitute a head positioning device operable to position each component-holding head <b>130</b>, in the form of a turning device <b>132</b> operable to turn each component-holding head <b>130</b> about the axis of rotation of the indexing table <b>120</b>. Further, the turning device <b>132</b> cooperates with the component-supply-device positioning device <b>48</b> and the board positioning device <b>64</b> to constitute a relative-movement device <b>134</b> operable to move each component-holding head <b>130</b>, the component supply device <b>14</b> and the PWB support device <b>184</b> relative to each other. The turning device <b>132</b> functions as an intermittently turning device operable to intermittently turn each component-holding head <b>130</b> about a vertical axis. The X-axis direction is parallel to a direction of tangency to the circular turning path of each component-holding head <b>130</b>, at the component receiving position <b>130</b>A. The component supply tables <b>30</b>, <b>32</b> of the component supply device <b>14</b> are moved by the component-supply-device positioning device <b>48</b>, in the above-indicated direction of tangency, such that the component-supply portions <b>37</b> of the tape feeders <b>36</b> are moved in this direction of tangency, namely, in the X-axis direction, and are stopped at a position corresponding to the component receiving position <b>130</b>A.

A supporting member <b>146</b> which supports each component-holding head <b>130</b> is vertically movably supported by the indexing disk <b>120</b>. A cam follower in the form of a roller <b>148</b> fixed to the supporting member <b>146</b> is held in engagement with a cam groove formed in a cylindrical cam <b>140</b> fixed to the frame <b>110</b>. The cam groove is formed in the cylindrical cam <b>140</b> such that the vertical position of the cam groove gradually changes in the circumferential direction of the cylindrical cam <b>140</b>, so that the roller <b>148</b> in rolling contact with the side surfaces of the cam groove is vertically moved to lift and lower the supporting member <b>146</b> and the component-holding head <b>130</b> as the component-holding head <b>130</b> is turned with the indexing disk <b>120</b> about the axis of the rotary shaft <b>112</b>. In the present embodiment, the cam groove is formed so that each component-holding head <b>130</b> is placed at its upper stroke end when the head <b>130</b> is stopped at its component receiving position <b>130</b>A, and is placed at its lower stroke end when the head <b>130</b> is stopped at its component mounting position <b>130</b>F, and so that the head <b>130</b> is moved horizontally when the head <b>130</b> is turned near the component receiving and mounting positions <b>130</b>A and <b>130</b>F along the circular path.

A support member in the form of a cylindrical sleeve <b>160</b> is fixed to the outer surface of the supporting member <b>146</b>. A shaft member <b>162</b> having a circular shape in transverse cross section is fitted in the cylindrical sleeve <b>160</b> such that the shaft member <b>162</b> is rotatable about a vertical axis (an axis of rotation of each suction nozzle <b>190</b> described below) relative to the cylindrical sleeve <b>160</b> and is axially movable together with the cylindrical sleeve <b>160</b>. A first engaging member <b>174</b> is connected to the shaft member <b>162</b> through a rotation transmitting shaft <b>164</b> such that the first engaging member <b>174</b> is rotatable with the shaft member <b>162</b> and is axially movable relative to the shaft member <b>162</b>. The first engaging member <b>174</b> is held stationary in the axial direction of the component-holding head <b>130</b> even when the head <b>130</b> is vertically moved by the roller <b>148</b> held in engagement with the cam groove of the cylindrical cam <b>140</b> while the head <b>130</b> is turned with the indexing disk <b>120</b>. Namely, the first engaging member <b>174</b> is not vertically moved while the shaft member <b>162</b> is vertically moved with the cylindrical sleeve <b>160</b> by the supporting member <b>146</b>.

The first engaging member <b>174</b> can be turned by a turning device including an externally toothed ring gear <b>176</b>, about the axis of rotation of the indexing disk <b>120</b>. Since the first engaging member <b>174</b> is flexibly connected to the shaft member <b>162</b> through a flexible-joint mechanism, the first engaging member <b>174</b> can be turned at a higher angular velocity than the indexing disk <b>120</b>, so that the first engaging member <b>174</b> reaches each working position of each component-holding head <b>130</b> before the head <b>130</b> reaches each working position, as disclosed in JP-A-6-342998. Since, this aspect of the first engaging member <b>174</b> regarding its movement relative to the component-holding head <b>130</b> does not directly relate to the present invention, no further description in this respect is deemed necessary.

The shaft member <b>162</b> has a lower end portion which extends downwards from the sleeve <b>160</b> and which carries an attaching member <b>184</b> fixed thereto. A rotary nozzle holder <b>186</b> is supported by the attaching member <b>184</b>, such that the rotary nozzle holder <b>186</b> is supported by a support shaft <b>188</b> (FIG. 6) rotatably about a horizontal axis perpendicular to the axis of the shaft member <b>162</b>.

The rotary nozzle holder <b>186</b> includes a plurality of nozzle holders <b>192</b>, more precisely, six nozzle holders <b>192</b>, which are arranged equiangularly about the axis of rotation of the rotary nozzle holder <b>186</b> (about the support shaft <b>188</b>). The six nozzle holders <b>192</b> are arranged to hold the respective six suction nozzles <b>190</b> such the suction nozzles <b>190</b> extend in the radial directions of the support shaft <b>188</b> at a predetermined angular interval. The rotary nozzle holder <b>186</b> is rotated about the support shaft <b>188</b> by a nozzle-holder selecting device (not shown) disposed near the above-indicated nozzle-holder selecting position, to bring a selected one of the six nozzle holders <b>192</b> into an operating or working position. In the operating position, the suction nozzle <b>190</b> held by the selected nozzle holder <b>192</b> faces downwards, and the axis of the suction nozzle <b>190</b> is aligned with the axis of the shaft member <b>162</b>. With the nozzle holder <b>192</b> placed in the operating position, the suction nozzle <b>190</b> held by the nozzle holder <b>192</b> is placed in its operating position for holding and releasing the electronic component <b>38</b>.

In the present embodiment, the shaft member <b>162</b>, the attaching member <b>184</b> and the rotary nozzle holder <b>186</b> constitute each component-holding head <b>130</b> which holds the six suction nozzles <b>190</b>. The component-holding head <b>130</b> is rotatable about the vertically extending axis of the shaft member <b>162</b> parallel to the axis of rotation of the indexing disk <b>120</b>, and is arranged to hold the selected suction nozzle <b>190</b> placed in its operating position such that the selected suction nozzle <b>10</b> extends substantially in its axial direction. The component-holding head <b>130</b> may be considered to be constituted by the nozzle holder <b>192</b> holding the selected suction nozzle <b>190</b> placed in the operating position, the attaching member <b>184</b> and the shaft member <b>162</b>.

The 16 component-holding heads <b>130</b> are identified by respective codes of head-code data, and the six nozzle holders <b>192</b> of each component-holding head <b>130</b> are also identified by respective codes of nozzle-holder-code data. Suction nozzle data indicative of the kinds of the suction nozzles <b>190</b> held by the respective nozzle holders <b>192</b> of each component-holding head <b>130</b> are stored in a ROM <b>404</b> of a control device <b>400</b> (which will be described), so that the specific kind of the selected suction nozzle <b>190</b> placed in its operating position of each component-holding head <b>130</b> can be identified on the basis of the above-indicated head-code data and nozzle-holder-code data, and the suction nozzle data.

Each component-holding head <b>130</b> and the suction nozzles <b>190</b> held by the head <b>130</b> cooperate to constitute a component mounting unit <b>194</b>. Namely, the component mounting device <b>16</b> has 16 component mounting units <b>194</b> arranged equiangularly in the circumferential direction of the indexing disk <b>120</b>. In FIG. 2, only two of the six suction nozzles <b>190</b> are shown for each of only two of the 16 component-holding heads <b>130</b>, in the interest of simplification. The opening <b>26</b> of a selected one of the tape feeders <b>36</b> of the component supply device <b>14</b> is located below the selected suction nozzle <b>190</b> (placed in its operating position) of the component-holding head <b>130</b> located at the component receiving position. At the component supply position of the selected tape feeder <b>36</b>, its component-supply portion <b>37</b> is located below the selected suction nozzle <b>190</b> of the component-holding head <b>130</b> located at the component receiving position, so that the electric component <b>38</b> is transferred from the component-supply portion <b>37</b> to the selected suction nozzle <b>190</b>.

Each of the six suction nozzles <b>190</b> held by each component-holding head <b>130</b> is arranged to hold the electronic component <b>38</b> by suction under a negative pressure. One of the suction nozzles <b>190</b> is shown in FIG. <b>6</b>. Each suction nozzle <b>190</b> includes a nozzle body <b>198</b>, and a suction pipe <b>200</b> the lower or free end face of which provides a sucking surface <b>201</b> for sucking the electronic component <b>38</b>, as shown in FIG. <b>6</b>. The suction nozzle <b>190</b> is removably held at its nozzle body <b>198</b> by the corresponding nozzle holder <b>192</b> such that the suction nozzle <b>190</b> is rotatable with the nozzle holder <b>192</b> and axially movable relative to the nozzle holder <b>192</b>. When the electronic component <b>38</b> is sucked by the suction nozzle <b>190</b> or transferred from the suction nozzle <b>190</b> onto the printed-wiring board <b>60</b>, the suction nozzle <b>190</b> is axially movable relative to the nozzle holder <b>192</b>, with compression of a spring <b>202</b> interposed as a biasing device between the rotary nozzle holder <b>186</b> and the suction nozzle <b>190</b>. The axial movement of the suction nozzle <b>190</b> relative to the nozzle holder <b>192</b> reduces an impact upon abutting contact of the suction nozzle <b>190</b> with the electronic component <b>38</b> or upon abutting contact of the electronic component <b>38</b> with the printed-wiring board <b>60</b>. In the present embodiment, the six suction nozzles <b>190</b> held by each component-holding head <b>130</b> are different in kind from each other, but have the same length so that the sucking surfaces <b>201</b> of all the suction nozzles <b>190</b> lie substantially on a circle whose center lies on the axis of rotation of the rotary nozzle holder <b>186</b>.

The selected suction nozzle <b>190</b> placed in its operating position is selectively communicated with a vacuum pump serving as a negative pressure source, an air pump serving as a positive pressure source, and the atmosphere. The electronic component <b>38</b> is sucked by the selected suction nozzle <b>190</b> when a negative pressure is applied form the vacuum pump to the suction nozzle <b>190</b>. When a positive air pressure is applied from the air pump to the suction nozzle <b>190</b>, the electronic component <b>38</b> is released from the suction nozzle <b>190</b>. Selective communication of the suction nozzle <b>190</b> with the vacuum pump, air pump and atmosphere is affected by a mechanical switching action of a control valve in the form of a directional control valve <b>220</b> (FIG. 2) attached to the cylindrical sleeve <b>160</b>.

As shown in FIG. 2, two head lifting and lowering devices <b>230</b>, <b>232</b> are provided in respective portions of the frame <b>110</b> and the cylindrical cam <b>140</b>, which portions correspond to the component receiving position <b>130</b>A and the component mounting position <b>130</b>F, respectively. Each head lifting and lowering device <b>230</b>, <b>232</b> serves as an axial-nozzle-movement device operable to move the component-holding head <b>130</b> and the selected suction nozzle <b>190</b> in the axial direction, and as a device operable to move the component supply device <b>14</b> and the component-holding head <b>130</b> in the axial direction of the head <b>130</b> toward and away from each other.

The head lifting and lowering device <b>230</b> disposed at the component receiving position <b>130</b>A will be briefly described by reference to FIG. <b>2</b>. The head lifting and lower device <b>230</b> includes a movable member in the form of a vertically movable member <b>238</b> and a vertical drive device <b>240</b> operable to lift and lower the vertically movable member <b>238</b>. The vertically movable member <b>238</b> is fitted in a guide groove <b>244</b> formed in the cylindrical cam <b>140</b> so as to extend in the axial direction of the indexing disk <b>120</b>, such that the vertically movable member <b>238</b> is movable in the axial direction of the indexing disk <b>120</b>. The vertically movable member <b>238</b> has, in its lower end portion, an engaging groove <b>252</b> which can be contiguous with the above-indicated cam groove formed in the cylindrical cam <b>140</b>. When the vertically movable member <b>238</b> is placed at its upper stroke end, the engaging rove <b>252</b> becomes contiguous with the cam groove so that the roller <b>148</b> moves into the engaging groove <b>238</b>, whereby the component-holding head <b>130</b> at the component receiving position <b>130</b>A is supported by the vertically movable member <b>238</b>.

The vertical drive device <b>240</b> includes a drive source in the for of the intermittent rotary drive motor <b>116</b> (FIG. <b>8</b>), a motion converting device operable to convert a rotary motion of the intermittent rotary drive motor <b>116</b> into a vertical movement, and a motion transmitting device operable to transmit the vertical movement to the vertically movable member <b>238</b>. The motion converting device includes a can in the form of a rotary cam <b>254</b>, a cam follower in the form of a roller <b>256</b>, and levers <b>258</b>, <b>260</b>. The motion transmitting device includes a connecting rod <b>262</b> and a spherical joint <b>264</b>. Thus, the vertically movable member <b>238</b> is vertically moved by the vertical drive device <b>240</b>, to lift and lower the component-holding head <b>130</b> and the selected suction nozzle <b>190</b>. The vertical movement of the suction nozzle <b>190</b> and its turning movement about the axis of the indexing disk <b>120</b> in timed relation with each other are controlled by the configurations of the cam used in the rotary drive device <b>114</b> and the rotary cam <b>254</b>. The vertical operating stroke of the vertically movable member <b>238</b> is adjusted to adjust the lowermost position of the component-holding head <b>130</b>. Since this adjustment does not directly relate to the present invention, no further description in this respect is deemed necessary.

The vertically movable member <b>238</b> of the head lifting and lowering device <b>232</b> is not adjustable in its vertical operating stroke. Namely, the lowermost and uppermost positions of he component-holding head <b>130</b> at the component mounting position <b>130</b>F are kept constant. In the other aspects, the lifting and lowering device <b>232</b> is identical with the lifting and lowering device <b>230</b>. The same reference signs as used for the lifting and lowering device <b>230</b> are used for the functionally corresponding elements of the lifting and lowering device <b>232</b>, which will not be described.

A component attitude changing device, a component hold-position rectifying device and an angular-head-position resetting device <b>300</b> (FIG. 5) are disposed at the component attitude changing position <b>130</b>C, the component hold-position rectifying position <b>130</b>E and the angular-head-position resetting device, respectively. The component attitude changing device is operated where the component-mounting angular position of the electronic component <b>38</b> in which the electronic component <b>38</b> is mounted on the printed-wiring board <b>60</b> is different from the component-receiving angular position in which the electronic component <b>38</b> is transferred from the component-supply portion <b>37</b> of the selected tape feeder <b>36</b> to the suction nozzle <b>190</b>. The component attitude changing device is arranged to rotate the component-holding head <b>130</b> holding the electronic component <b>38</b> about its axis, to establish the component mounting angular position of the electronic component <b>38</b>. The component hold-position rectifying device is arranged to rotate the component-holding head <b>130</b> about its axis, for rotating the selected suction nozzle <b>190</b> to adjust the angular position of the electronic component <b>38</b> as held by the suction nozzle <b>190</b>, for an error of angular positioning of the electronic component <b>38</b> about an axis perpendicular to the sucking surface <b>201</b>. The angular-head-position resetting device <b>300</b> is arranged to rotate the component-holding head <b>130</b> to its angular zero position after the head <b>130</b> has been rotated by the component attitude changing device and/or the component hold-position rectifying device. The component-holding head <b>130</b> is placed in the angular zero position when it is located at the component receiving position <b>130</b>A.

The component attitude changing device, the component hold-position rectifying device and the angular-head-position resetting device <b>300</b> are all head rotating devices which are identical in construction with each other, in the present embodiment. Referring to FIG. 5, the angular-head-position resetting device <b>300</b> will be described by way of example. The resetting device <b>300</b> includes a second engaging member <b>304</b> supported by the frame <b>110</b> such that the second engaging member <b>304</b> is axially movable and rotatable relative to the frame <b>110</b>. The resetting device <b>300</b> further includes a vertically moving device <b>306</b> and a rotating device <b>308</b>. The vertically moving device <b>306</b> is arranged to move the second engaging member <b>304</b> in its axial direction, namely, in the vertical direction parallel to the axis of rotation of the indexing disk <b>120</b>, for engagement and disengagement of the second engaging member <b>304</b> with and from the first engaging member <b>174</b> described above. The rotating device <b>308</b> is arranged to rotate the second engaging member <b>304</b>.

The vertically moving device <b>306</b> includes a motion converting device including a cam and a cam follower for converting he rotary motion of the intermittent rotary drive motor <b>116</b> into a vertical movement, and a motion transmitting mechanism for converting the vertical movement to the second engaging member <b>304</b> for engagement and disengagement with and from the first engaging member <b>174</b>. The rotating device <b>308</b> includes an angular-head-position resetting motor <b>310</b> (FIG. <b>8</b>), rotary motion of which is transmitted to the second engaging member <b>304</b> through a motion transmitting device including a timing pulley <b>312</b>, so that the second engaging member <b>304</b> is rotated about its vertically extending axis. The second engaging member <b>304</b> in engagement with the first engaging member <b>174</b> is rotated, so that a rotary motion of the second engaging member <b>304</b> is transmitted to the component-holding head <b>130</b> through the first engaging member <b>174</b> and the rotation transmitting shaft <b>164</b>. Thus, the head <b>130</b> can be rotated by a desired angle in a selected one of the clockwise and counterclockwise directions.

The angular-head-position resetting device <b>300</b> is provided with a first angular-zero-position detecting device <b>320</b> for detecting the angular zero position of the second engaging member <b>304</b>. The first angular-zero-position detecting device <b>320</b>, which is attached to the frame <b>110</b>, consists of a sensor of optical fiber type arranged to detect the angular zero position of the member <b>304</b>, depending upon whether a light is reflected from a reflecting member <b>324</b> disposed on the timing pulley <b>312</b>. A detecting device similar to the first angular-zero-position detecting device <b>320</b> is provided on the component attitude changing device and the component hold-position rectifying device.

The angular-head-position resetting device <b>300</b> is also provided with a second angular-zero-position detecting device <b>330</b> for detecting the angular zero position of the component-holding head <b>130</b>. The detecting device <b>330</b> consists of a sensor of optical fiber type arranged to detect the angular zero position of the component-holding head <b>130</b>, depending upon a light is reflected from a reflecting member <b>332</b> disposed on the outer circumferential surface of the first engaging member <b>174</b>, which is fixed at the upper end of the rotation transmitting shaft <b>164</b> which is rotatable with the component-holding head <b>130</b>. The second angular-zero-position detecting device <b>330</b> is provided for the angular-head-position resetting device <b>300</b>. The component-holding head <b>130</b> is placed in its angular zero position when the head <b>130</b> located at the component receiving position <b>130</b>A receives the electronic component <b>38</b> from the component supply device <b>14</b>. When the component-holding head <b>130</b> is located at the angular-head-position resetting position <b>130</b>G, the head <b>130</b> is rotated by the angular-head-position resetting device <b>300</b>, to its angular zero position, namely, to its component-receiving angular position in which the head <b>130</b> is located at the component receiving position <b>130</b>A. The detection of the angular zero position of the head <b>130</b> by the second angular-zero-position detecting device <b>330</b> assures that the head <b>130</b> is placed in its angular zero position or component-receiving angular position when the head <b>130</b> receives the electronic component <b>38</b> at the component receiving position <b>130</b>A. Where the head <b>130</b> is not placed in its angular zero position when the head <b>130</b> is located at the component receiving position <b>130</b>A, an alarm indicator is activated, or any other suitable measure is taken.

In the present embodiment, the first and second engaging members <b>174</b>, <b>340</b> are engageable with each other at two angular positions which are spaced from each other by 180°. The first angular-zero-position detecting device <b>320</b> is adapted to detect the light reflected by the reflecting member <b>324</b> when the second engaging member <b>304</b> is placed in a predetermined one of the two angular positions in which the second engaging member <b>304</b> is engageable with the first engaging member <b>174</b> of the component-holding head <b>130</b> placed in the angular zero position. This predetermined angular position of the second engaging member <b>304</b> is the angular zero position of the member <b>304</b>. The first angular-zero-position detecting device <b>320</b> provided for each of the component attitude changing device and the component hold-position rectifying device is adapted to detect the light reflected from the reflecting member <b>324</b> of the second engaging member <b>304</b> placed in the angular position for engagement with the first engaging member <b>174</b> corresponding to the component-holding head <b>130</b> placed in the angular zero position when this head <b>130</b> is located at the component attitude changing position <b>130</b>C or component hold-position rectifying position <b>130</b>E.

At the component hold-position detecting position, there are disposed two component cameras <b>350</b>, <b>352</b>, a waveguide device <b>354</b> and an illuminating device <b>356</b>, as shown in FIG. <b>7</b>. These component cameras <b>350</b>, <b>352</b>, waveguide device <b>354</b> and illuminating device <b>356</b> constitute an image-taking device <b>358</b>. The component cameras <b>350</b>, <b>352</b>, which are constructed as disclosed in JP-A-5-196441, will be described only briefly.

Like the fiducial mark camera <b>90</b>, each of the component cameras <b>350</b>, <b>352</b> is a CCD camera which includes CCDs and a lens system and which is an image-taking device in the form of a surface-imaging device capable of taking a two-dimensional image of an object at one time. Each component camera <b>350</b>, <b>352</b> has an imaging area perpendicular to its centerline and having a center lying on its centerline. The two component cameras <b>350</b>, <b>352</b> have respective different ratios or times of magnification. The component camera <b>350</b> has a comparatively low magnification ratio but has a comparatively wide field of view, while the component camera <b>350</b> has a comparatively high magnification ratio but has a comparatively narrow field of view. The two component cameras <b>350</b>, <b>352</b> are selectively used depending upon the size of the electronic component <b>38</b>.

The two component cameras <b>350</b>, <b>352</b> are supported by a circumferential portion of the frame <b>110</b> which is located radially outwardly of the indexing disk <b>120</b> and which corresponds to the component hold-position detecting position. The two component cameras <b>350</b>, <b>352</b> are positioned radially outwardly of the indexing disk <b>120</b> and the component-holding head <b>130</b> located at the component hold-position detecting position, such that the centerlines of the cameras <b>350</b>, <b>352</b> are parallel to each other and parallel to the vertically extending axis of rotation of the indexing disc <b>120</b> and are located on a straight line passing the axis of rotation of the indexing disc <b>120</b> and the axis of rotation of the component-holding head <b>130</b> located at the component hold-position detecting position, and such that the two component cameras <b>350</b>, <b>352</b> face downwards, so that an image of an object is formed in the horizontal imaging area. Position adjusting devices (not shown) are provided to adjust the positions of the two component cameras <b>350</b>, <b>352</b> in the radial and circumferential directions of the indexing disk <b>120</b> in the horizontal plane perpendicular to the centerlines of the cameras <b>350</b>, <b>352</b>, and the angular positions of the cameras <b>350</b>, <b>352</b> about their centerlines. The adjustment of the positions of the component cameras <b>350</b>, <b>352</b> will be described later.

At the component hold-position detecting position, the waveguide device <b>354</b> is disposed so as to extend from a position right below the component-holding head <b>130</b> located at the component hold-position detecting position, to positions right below the lower ends of the component cameras <b>350</b>, <b>352</b>. The waveguide device <b>354</b> includes reflecting mirrors for reflecting a light indicative of images of the electronic component <b>38</b> held by the suction nozzle <b>190</b> and other objects, to be incident upon the component cameras <b>350</b>, <b>352</b>. Thus, the image of the electronic component <b>38</b> is taken by the component cameras <b>350</b>, <b>352</b>, in the upward direction toward the electronic component <b>38</b>.

The illuminating device <b>356</b> provided in the present embodiment is arranged to selectively irradiate the suction nozzle <b>190</b> with a visible light or a ultraviolet radiation, to take a silhouette image or a front image of the object. When the suction nozzle <b>190</b> is irradiated with the visible light, the visible light is reflected by the electronic component <b>38</b> held by the suction nozzle <b>190</b>, so that a front image of the electronic component <b>38</b> is taken. When the suction nozzle <b>190</b> is irradiated with the ultraviolet radiation, the ultraviolet radiation is absorbed by a light emitting surface <b>360</b> provided on the suction nozzle <b>190</b>, and the light emitting surface <b>360</b> emits a visible light with which the upper surface of the electronic component <b>38</b> is irradiated so that a silhouette image of the electronic component <b>38</b> is taken. The light emitting surface <b>360</b> is coated with a fluorescent material for converting the ultraviolet radiation into the visible light. The component cameras <b>350</b>, <b>352</b>, waveguide device <b>354</b> and illuminating device <b>356</b> cooperate to constitute an imaging system.

In the electronic-component mounting system <b>12</b> according to the present embodiment, there is established by the XY coordinate system wherein the X-axis and Y-axis directions are respectively parallel to the horizontal and vertical directions as seen in the plan views of FIGS. 1 and 4 wherein the component supply device <b>14</b> is located above the PWB support device <b>18</b>, as described above. The upward and rightward directions as seen in FIG. 4 are positive X-axis and Y-axis directions, respectively. The XY plane is the horizontal plane. On the other hand, the imaging area of each component camera <b>350</b>, <b>352</b>, there is established an XY coordinate system wherein the Y-axis direction is parallel to the horizontal straight line which passes the axis of rotation of the indexing disk <b>120</b> and the axis of rotation of the component-holding head <b>130</b> located at the component hold-position detecting position, as indicated in FIG. 4, while the X-axis direction is perpendicular to the Y-axis direction in the horizontal plane. In the XY coordinate system of the component cameras <b>350</b>, <b>352</b>, the radially inward direction of the indexing disk <b>120</b> is a positive Y-axis direction, while the direction corresponding to the counterclockwise direction at the component hold-position detecting position as seen in FIG. 4 is a positive X-axis direction.

As described below, various positioning errors such as the positioning error of the electronic component <b>38</b> as held by the suction nozzle <b>190</b> are detected on the basis of the images of the electronic component <b>38</b>, etc. taken by the component cameras <b>350</b>, <b>352</b>, for compensating the movement data of the PWB support device <b>18</b>, etc. Those positioning errors detected at the component hold-position detecting position must be converted into positioning errors at the component receiving position <b>130</b>A and positioning errors at the component mounting position <b>130</b>F, depending upon a positional difference between the component hold-position detecting position and the component receiving position <b>130</b>A, and a positional difference between the component hold-position detecting position and the component mounting position <b>130</b>F.

For mounting the electronic component <b>38</b> on the printed-wiring board <b>60</b>, an image of the electronic component <b>38</b> as viewed in the downward direction is necessary. However, the image of the electronic component <b>38</b> is taken in the upward direction by the component cameras <b>350</b>, <b>352</b>. This must also be taken into account. An image of the object to be formed in the imaging area of each component camera <b>350</b>, <b>352</b> is rotated 180° about the X axis with respect to the downward orientation of the camera <b>350</b>, <b>352</b>. Accordingly, the attitude of the image of the object taken by the component camera <b>350</b>, <b>352</b> in the upward direction is the same in the X-axis direction as that of an image taken in the downward direction, but is reversed in the Y-axis direction to that of the latter image, with respect to the X axis. This reversal of the image in the Y-axis direction must also be taken into account when the movement data of the PWB support device <b>18</b>, etc. are compensated for the various positioning errors detected on the basis of the images of the electronic component <b>38</b>, etc.

The present electronic-component mounting system <b>12</b> includes a control device <b>400</b> illustrated in FIG. <b>8</b>. The control device <b>400</b> is constituted principally by a computer <b>410</b> incorporating a processing unit (PU) <b>402</b>, a read-only memory (ROM) <b>404</b>, a random-access memory (RAM) <b>406</b>, and a bus interconnecting the elements <b>402</b>, <b>404</b>, <b>406</b>. To the bus, there is connected an input/output interface <b>412</b> to which are connected the first angular-zero-position detecting device <b>320</b>, the second angular-zero-position detecting device <b>330</b>, and various sensors such as an encoder <b>420</b>.

To the input/output interface <b>412</b>, there are also connected the support block drive motor <b>42</b> and various other actuators <b>68</b>, <b>76</b>, <b>116</b>, <b>310</b> through respective driver circuits <b>416</b>. These actuators <b>42</b>, <b>68</b>, <b>76</b>, <b>116</b>, <b>310</b> serving as drive sources are electric motors, more specifically, rotary electric motors in the form of servomotors the amounts of operation of which can be controlled with high accuracy. Stepping motors rather than the servomotors may be used as those actuators. The operating amounts of the actuators <b>42</b>, etc. are detected by respective rotary encoders the output signals of which are used to control the actuators. Of these encoders, only the encoder <b>420</b> for the support block drive motor <b>42</b> is shown in FIG. <b>8</b>.

To the interface <b>412</b>, there are also connected the fiducial mark camera <b>90</b> and the component cameras <b>350</b>, <b>352</b> through respective control circuits <b>418</b>. The driver circuits <b>416</b>, control circuits <b>418</b> and computer <b>410</b> constitute the control device <b>400</b>. The RAM <b>406</b> is used to store various control programs which are down-loaded from a host computer, for instance, and to temporarily store various kinds of data. The control programs include a control program for mounting the electronic component <b>38</b> on the printed-wiring board <b>60</b>, a control program for detecting the position of the rotation axis of the component-holding head <b>130</b>, and a control program for detecting the positioning error of the sucking surface <b>201</b> of the suction pipe <b>200</b>.

Basic operations of the electronic-component mounting system <b>12</b> to mount the electronic component <b>38</b> on the printed-wiring board <b>60</b> are well known in the art, as disclosed in JP-B2-8-21791, and will be briefly described.

When the electric component <b>38</b> is mounted on the printed-wiring board <b>60</b>, the component-holding head <b>130</b> located at the component receiving position <b>130</b>A is lifted by the head lifting and lowering device <b>230</b>, so that the selected suction nozzle <b>190</b> placed in its operating position picks up the electronic component <b>38</b> by suction. At this time, the component-holding head <b>130</b> located at the component receiving position <b>130</b>A is placed in its angular zero position, for the selected suction nozzle <b>190</b> to receive the electronic component <b>38</b> from the component-supply portion <b>37</b>. Then, the component-holding head <b>130</b> is stopped at the component upright attitude detecting position <b>130</b>B to determine whether the electronic component <b>38</b> held by the suction nozzle <b>190</b> stands upright with one of its side faces in contact with the sucking surface <b>201</b> of the suction pipe <b>200</b>. Normally, the electronic component <b>38</b> lies flat with one of its opposite major surfaces in contact with the sucking surface <b>201</b>. At the component attitude changing position <b>130</b>C, the angular position of the electronic component <b>38</b> is changed if necessary to establish the predetermined component-mounting angular position, by rotating the component-holding head <b>130</b> from its angular zero position. Before the component-holding head <b>130</b> is rotated, the second engaging member <b>304</b> placed in the angular zero position is brought into engagement with the first engaging member <b>170</b> of the head <b>130</b> placed in the angular zero position, so that the head <b>130</b> can be rotated by the rotating device <b>308</b>.

When the component-holding head <b>130</b> is stopped at the component hold-position detecting position <b>130</b>D, an image of the electronic component <b>38</b> is taken by one of the component cameras <b>350</b>, <b>352</b>. The image of the electronic component <b>38</b> taken is compared with a reference or nominal image, to calculate XY positioning errors ΔXE and ΔYE and an angular positioning error Δθ of the electronic component <b>38</b>. The XY positioning errors ΔXE and ΔYE are X-axis and Y-axis errors of a predetermined sucking position <b>38</b>A of the electronic component <b>38</b> with respect to the axis of rotation of the component-holding head <b>130</b> in the XY or horizontal plane, as described below in detail by reference to FIG. 13, while the angular positioning error Δθ is an error of the angular position of the electronic component <b>38</b> about a vertical axis perpendicular to the sucking surface <b>201</b> of the suction nozzle <b>190</b>. At the component hold-position rectifying position <b>130</b>E, the suction nozzle <b>190</b> is rotated by the component hold-position rectifying device, to adjust the angular position of the electronic component <b>38</b> for compensation for the angular positioning error Δθ. If the angular position of the electronic component <b>38</b> has been changed at the component attitude changing position <b>130</b>C, the second engaging member <b>304</b> of the component hold-position rectifying device is rotated to an angular position in which the second engaging member <b>304</b> is engageable with the first engaging member <b>174</b> of the component-holding head <b>130</b> which has been rotated at the component attitude changing position <b>130</b>C. If the angular position of the electronic component <b>38</b> has not been changed at the component attitude changing position <b>130</b>C, the second engaging member <b>304</b> placed in its angular zero position is engageable with the first engaging member <b>174</b>, for rotating the head <b>130</b> at the component hold-position rectifying position <b>130</b>E. The compensation of the angular position of the electronic component <b>38</b> for the angular positioning error Δθ is affected while taking into account the positional difference between the component hold-position detecting position <b>130</b>D and the component hold-position rectifying position <b>130</b>E, and the reversal in the Y-axis direction of the image of the electronic component <b>38</b> taken by the component camera <b>350</b>, <b>352</b> in the upward direction.

Distances of movements of the PWB support device <b>18</b> in the X-axis and Y-axis directions for mounting the electronic component <b>38</b> on the printed-wiring board <b>60</b> are adjusted for compensation for the XY positioning errors ΔXE and ΔYE. The PWB support device <b>18</b> is moved by the board positioning device <b>64</b> to move the printed-wiring board <b>60</b> so that a component mounting position <b>130</b>F on the board <b>60</b> at which the electronic component <b>38</b> is to be mounted is aligned with the component mounting position <b>130</b>F of the component-holding head <b>130</b>. The movement distances of the PWB support device <b>18</b> are compensated for the XY positioning errors ΔXE and ΔYE. This compensation is affected while taking into account the XY positioning errors ΔXP and ΔYP of the printed-wiring board <b>60</b>, and the positioning error of the sucking position <b>38</b>A of the electronic component <b>38</b> which has been caused by the angular position adjustment at the component hold-position rectifying position <b>130</b>E for compensation for the angular positioning error Δθ. The XY positioning errors ΔXP and ΔYP of the component mounting position <b>130</b>F on the printed-wiring board <b>60</b> are calculated on the basis of XY positioning errors of the board <b>60</b> which have been obtained on the basis of an image of the fiducial mark <b>88</b> on the board <b>60</b> taken by the fiducial mark camera <b>90</b> prior to the mounting operation of the electronic component <b>38</b>. The positioning error of the sucking position <b>38</b>A of the electronic component <b>38</b> due to the adjustment of its angular position is obtained on the basis of the position of the rotation axis A of the selected suction nozzle <b>190</b>, and the angular positioning error Δθ and the XY positioning errors of the electronic component <b>38</b>. The manner of obtaining the position of the rotation axis A of the suction nozzle <b>190</b> will be described later. The adjustment of the movement distances of the PWB support device <b>18</b> is affected while taking into account the positional difference between the component hold-position detecting position <b>130</b>D and the component mounting position <b>130</b>F, and the reversal in the Y-axis direction of the image of the electronic component <b>38</b> taken by the component camera <b>350</b>, <b>352</b> in the upward direction.

At the component mounting position <b>130</b>F, the suction nozzle <b>190</b> is lowered by the head lifting and lowering device <b>232</b>, to mount the electronic component <b>38</b> onto the printed-wiring board <b>60</b>. Then, the component-holding head <b>130</b> is stopped at the angular-head-position resetting position <b>130</b>G at which the head <b>130</b> is rotated by the angular-head-position resetting device <b>300</b>, to its angular zero position or component-receiving angular position. At the angular-head-position resetting position <b>130</b>G, the second engaging member <b>304</b> of the angular-head-position resetting device <b>300</b> is rotated by an angle determined on the basis of the angular positioning error Δθ of the electronic component <b>38</b> and its angle of rotation to establish the component-mounting angular position, so that the second engaging member <b>304</b> is placed in an angular position in which the second engaging member <b>304</b> is engageable with the first engaging member <b>174</b>, for rotating the component-holding head <b>130</b> to its angular zero position.

When the suction nozzle <b>190</b> receives the electronic component <b>38</b> from the component supply device <b>14</b>, for mounting the electronic component <b>38</b> on the printed-wiring board <b>60</b>, as described above, the component supply table <b>30</b> or <b>32</b> of the components supply device <b>14</b> is moved by the table positioning device <b>46</b>, to bring the component-supply portion <b>37</b> of a selected one of the tape feeders <b>36</b> to the component supply position. The electronic components <b>38</b> are supplied in a predetermined order from the two or more tape feeders <b>36</b>, and the component supply table <b>30</b> or <b>32</b> is moved according to table movement data determined by the predetermined order of supply of the electronic components <b>38</b>, so that the component-supply portion <b>37</b> of the tape feeder <b>36</b> from which the electronic component <b>38</b> is to be supplied next is located at the component supply position right below the component-holding head <b>130</b> located at the component receiving position <b>130</b>A. The table movement data are defined in the XY coordinate system of the electronic mounting system <b>12</b>.

The X-axis position of the selected tape feeder <b>36</b> at which the electronic component <b>38</b> is picked up by the suction nozzle <b>190</b> is determined and adjusted on the basis of the predetermined sucking position <b>38</b>A of the electronic component <b>38</b>, the positioning error of the selected tape feeder <b>36</b>, the positioning error of the axis of rotation of the component-holding head <b>130</b> (hereinafter referred to as “head axis”), and the positioning error of the sucking surface <b>201</b> of the suction nozzle <b>190</b> with respect to the head axis, so that the electronic component <b>38</b> can be held by suction by the suction pipe <b>200</b>, with high stability and a minimum distance of deviation of the electronic component <b>38</b> in the X-axis direction in which the component supply table <b>30</b>, <b>32</b> is moved. The positioning error of the sucking surface <b>201</b> with respect to the head axis is caused by eccentricity of the suction pipe <b>200</b> with respect to the nozzle body <b>198</b>, and bending of the suction pipe <b>200</b>, although the suction pipe <b>200</b> and the nozzle body <b>198</b> are designed to be concentric with each other.

The predetermined sucking position <b>38</b>A of the electronic component <b>38</b> is known from the specific kind of the electronic component <b>38</b>, and the table movement data are prepared on the basis of the known sucking position <b>38</b>A of the electronic component <b>38</b>. The positioning error of the head axis and the positioning error of the sucking surface <b>201</b> with respect to the head axis are detected, and the table movement data are adjusted or modified on the basis of the detected positioning errors of the head axis and the sucking surface <b>201</b>. The detection of the positioning errors is affected while the electronic-component mounting system <b>12</b> is not in the component mounting operation, for instance, during manufacture, maintenance inspection or daily pre-operation inspection of the mounting system <b>12</b>, or upon replacement of the suction nozzle or nozzles <b>190</b>, or alternatively, during an interruption of a continuous component mounting operation. Where the positioning errors are detected during an interruption of the continuous component mounting operation, the detection is initiated when at least one predetermined condition of the mounting system <b>12</b> is satisfied. For instance, the detection is initiated when at least one of the following conditions is satisfied: that the cumulative operating time of the mounting system <b>12</b> has exceeded a predetermined threshold; that the number of the electronic components <b>38</b> which have been mounted on the printed-wiring board <b>60</b> has exceeded a predetermined threshold; and that the number of the printed-wiring boards <b>60</b> on which the electronic components <b>38</b> have been mounted has exceeded a predetermined threshold. However, it is not essential to initiate the detection of the positioning errors when the predetermined condition is satisfied. Further, any other condition in addition to the conditions described above by way of example may be used. If a given predetermined condition is satisfied before all of the predetermined electronic components <b>38</b> have been mounted on a given printed-wiring board <b>60</b>, for instance, the detection of the positioning errors may be initiated after the mounting of all of the electronic components <b>38</b> on that board <b>60</b> is completed. In this instance, the detection of the positioning errors may be considered to be initiated during an interruption of a continuous component mounting operation on a plurality of printed-wiring boards <b>60</b>. Alternatively, the detection of the positioning errors may be initiated by interrupting the continuous component mounting operation upon generation of a trigger signal from suitable commanding means. The commanding means may be an input device operable by the operator of the mounting system <b>12</b>, or means responsive to a command received from a host computer. The positioning errors detected during an interruption of the continuous component mounting operation include positioning errors caused by thermal expansion of the various parts of the mounting system <b>12</b> due to a temperature rise of those parts, or include a change in the positioning errors caused by the thermal expansion. The positioning error of each tape feeder <b>36</b> is detected on the basis of an image of the electronic component <b>38</b> held by the suction nozzle <b>190</b>, as described below, and the movement data used for positioning the component supply table <b>30</b>, <b>32</b> are adjusted or modified on the basis of the detected positioning error of the tape feeder <b>36</b>, when the relevant electric component <b>38</b> is mounted on the printed-wiring board <b>60</b>. There will be described the manner of detecting the positioning errors and the manners of preparing and adjusting the table movement data. In the present embodiment, the detection of the positioning errors and the preparation of the table movement data are affected upon a daily pre-operation inspection of the mounting system <b>12</b>, upon satisfaction of the predetermined condition, and upon replacement of the suction nozzles <b>190</b>. Initially, the detection of the positioning errors upon the daily pre-operation inspection will be described.

The sucking position <b>38</b>A of the electronic component <b>38</b>, which is one of the elements used to prepare and adjust the movement data for the tape feeder <b>36</b>, is determined depending upon the specific shape and dimensions of each electronic component <b>38</b>, for each kind of the electronic component <b>38</b>. According to the thus determined sucking position <b>38</b>A of each electronic component <b>38</b>, the table movement data are prepared. Alternatively, standard table movement data prepared without taking account of the sucking position <b>38</b>A of the specific electronic component <b>38</b> may be modified on the basis of the sucking position <b>38</b>A of the specific electronic component <b>38</b>.

The predetermined sucking position <b>38</b>A of the specific electronic component <b>38</b> is a portion of that electronic component <b>38</b> at which the electronic component <b>38</b> can be held by the suction nozzle <b>190</b> with the highest degree of stability. This portion (sucking position) is not necessarily a central portion of the electronic component <b>38</b>, and may be offset from the center position of an ordinary electronic component, as indicated in FIG. <b>9</b>. The ordinary electronic component, which has a rectangular or square shape in transverse cross section, has its center position which is a midpoint in both of the width direction and the length direction. In the present application, the reference sign <b>38</b> denotes all kinds of electronic components, namely, the ordinary electronic components and the other electronic components. The carrier tape <b>22</b> is held by the tape feeder <b>36</b> such that the center of the ordinary electronic component <b>38</b> as seen in the width direction (in the X-axis direction) is located at the center of the opening <b>26</b> of the covering member <b>24</b> as seen in the X-axis direction. Where the electronic component is not the ordinary electronic component <b>38</b>, the predetermined sucking position <b>38</b>A is offset from the center position of the ordinary electronic component <b>38</b> by an offset distance ΔXB in the X-axis direction. That is, the predetermined sucking position <b>38</b>A of the electronic component <b>38</b> is defined by the offset distance ΔXB of the sucking position <b>38</b>A to the widthwise center <b>38</b>C of the electronic component <b>38</b> in the X-axis direction. This offset distance ΔXB defining the sucking position <b>38</b>A is defined with a positive or negative sign, in the XY coordinate system established for the mounting system <b>12</b>. The table movement data are prepared according to the thus defined offset distance ΔXB. Although the position at which the electronic component <b>38</b> can be suitably sucked may be offset from the center of the electronic component <b>38</b> in the Y-axis direction, the sucking position <b>38</b>A is not set in the Y-axis direction, since the component supply tables <b>30</b>, <b>32</b> are movable in the X-axis direction only. The electronic component <b>38</b> is held by the suction nozzle <b>190</b>, at a Y-axis position determined by the component supply device <b>14</b>, so that the electric component <b>38</b> is sucked at its central portion. The sign of the value of the offset distance ΔXB is determined with the X-axis zero point being located at the center point of the electric component <b>38</b> in the XY coordinate system of the electric-component mounting system <b>12</b>. In FIG. 9, the opening <b>26</b> of the covering member <b>24</b> is only schematically shown.

There will next be described the manner of detecting the positioning error of the head axis (axis of rotation of the component-holding head <b>130</b>). To detect the positioning error of the head axis, one of the plurality of suction nozzles <b>190</b> held by one of the plurality of component-holding heads <b>130</b> is selected as a reference suction nozzle whose axis of rotation is used to detect the positioning errors of the head axis of the suction nozzles <b>190</b> other than the reference suction nozzle, since the axis of rotation of the reference suction nozzle is used as a basis for setting the zero positions of the various movable members or devices of the mounting system <b>12</b> such as the component supply tables <b>30</b>, <b>32</b> and the board positioning device <b>64</b>. Although all of the six suction nozzles <b>190</b> held by each component-holding head <b>130</b> theoretically have the same axis of rotation, the six suction nozzles <b>190</b> when placed in their operating position may have different axes of rotation due to a manufacturing error or for any other reason. In view of this, the positioning errors of the rotation axis of all of the suction nozzles <b>190</b> other than the reference suction nozzle are detected with respect to the rotation axis of the reference suction nozzle. Accordingly, the rotation axis of one suction nozzle <b>190</b> on one component-holding head <b>130</b> may differ from the rotation axis of another suction nozzle <b>190</b> on the same head <b>130</b>. The rotation axis of the presently selected suction nozzle <b>190</b> which is presently selected on the component-holding head <b>130</b> and which is placed in the operating position for mounting the electronic component <b>38</b> is used as the rotation axis of that head <b>130</b>.

Initially, the position of the axis of rotation of the reference suction nozzle is detected on the basis of two front images of the sucking surface <b>301</b> of the reference suction nozzle taken by each of the two component cameras <b>350</b>, <b>352</b> at respective two different angular positions of the relevant component-holding head <b>130</b>. Like the image electronic component <b>38</b> held by the suction nozzle <b>190</b>, the image of the sucking surface <b>201</b> of the reference suction nozzle at each of the two different angular positions is taken by each component camera <b>350</b>, <b>352</b> in the upward direction, that is, in the axial direction of the component-holding head <b>130</b> toward the sucking surface <b>201</b>. As described above, the component cameras <b>350</b>, <b>352</b> are positioned radially outwardly of the indexing disk <b>120</b> and the component-holding head <b>130</b> located at the component hold-position detecting position <b>130</b>D, and are oriented so as to face downwards. The light indicative of an image of the object such as the sucking surface <b>201</b> is guided by the waveguide device <b>354</b>, so as to be incident upon the component cameras <b>350</b>, <b>352</b>, so that the image is taken in the upward direction toward the object. In the present embodiment, the two different angular positions of the component-holding head <b>130</b> holding the reference suction nozzle <b>190</b> consist of the angular zero position established at the component receiving position <b>130</b>A (component-receiving angular position), and an angular position which is angularly spaced by 180° from the component-receiving angular position.

After the images of the sucking surface <b>201</b> of the reference suction nozzle <b>190</b> placed in the component-receiving angular position are taken by the component cameras <b>350</b>, <b>352</b>, the component-holding head <b>130</b> is moved to the angular-head-position resetting position <b>130</b>G by rotation of the indexing disk <b>120</b>. At this angular-head-position resetting position <b>130</b>G, the component-holding head <b>130</b> is rotated by 180° by the angular-head-position resetting device <b>300</b>, and the images of the sucking surface <b>201</b> are taken again by the component cameras <b>350</b>, <b>352</b>. Thus, the component-holding head <b>130</b> located at the angular-head-position resetting position <b>130</b>G is placed in the angular position of 180° with respect to the angular zero position, for the purpose of taking the images of the sucking surface <b>201</b> of the reference suction nozzle. Even if the second angular-zero-position detecting device <b>330</b> detects that the component-holding head <b>130</b> is not placed in the angular zero position at the angular-head-position resetting position <b>130</b>G, the angular-head-position resetting device <b>300</b> is not operated to establish the angular zero position before the images of the sucking surface <b>201</b> are taken.

FIG. 10A indicates an example of the first image of the sucking surface <b>201</b> of the reference suction nozzle <b>190</b> taken by the component camera <b>350</b> when the component-holding head <b>130</b> is located at the angular zero position, and FIG. 10B indicates not only the first image, but also an example of the second image of the sucking surface <b>201</b> also taken by the component camera <b>350</b> when the head <b>130</b> is located at the angular-head-position resetting position <b>130</b>G which is 180° apart from the angular zero position. Suppose a center point M<b>1</b> of the first image has X-axis and Y-axis coordinate values (x1, y1) while a center point M<b>2</b> of the second image has X-axis and Y-axis coordinate values (x2, y2), the axis of rotation A of the reference suction nozzle <b>190</b> is located at a midpoint between the two center points M<b>1</b>, M<b>2</b>, which has X-axis and Y-axis coordinate values {(x1+x2)/2, (y1+y2)/2}. Then, error distances ΔXA and ΔYA between the rotation axis A and a center of the imaging area <b>38</b>B of the component camera <b>350</b> are obtained and indicated on a suitable display device (not shown), so that the operator of the mounting system <b>12</b> can adjust the position of the component camera <b>350</b>, while observing the indicated error distances ΔXA and ΔYA, for alignment of the center of the imaging area <b>38</b>B with the rotation axis A of the reference suction nozzle <b>190</b>. In FIGS. 10A and 10B and the following figures, the images of the objects such as the sucking surface <b>201</b> are denoted by the same reference signs as used for the objects, in the interest of easier understanding. After the second image of the sucking surface <b>201</b> is taken, the component-holding head <b>130</b> is further rotated by 180° by the angular-head-position resetting device <b>300</b> at the angular-head-position resetting position <b>130</b>G, so that the head <b>130</b> is returned to its angular zero position or component-receiving angular position. Similarly, the first and second images of the sucking surface <b>201</b> of the reference suction nozzle <b>190</b> are taken by the component camera <b>352</b>, and the position of the component camera <b>352</b> in the horizontal plane is adjusted so as to eliminate the detected error distances between the rotation axis A of the reference suction nozzle <b>190</b> and the center of the imaging area <b>38</b>B of the component camera <b>352</b>.

After the positions of the component cameras <b>350</b>, <b>352</b> in the horizontal or XY plane perpendicular to their centerlines have been adjusted, the angular positions of the cameras <b>350</b>, <b>352</b> about their centerlines are adjusted. To adjust the angular positions of the component cameras <b>350</b>, <b>352</b>, a suitable adjusting jig (not shown) is fixed on one of the nozzle holders <b>192</b>, in place of the suction nozzle <b>190</b>. For example, the adjusting jig includes a mounting portion at which the adjusting jig is mounted on the nozzle holder <b>192</b>, and a reference-surface portion for adjusting the angular position of each component camera <b>350</b>, <b>352</b>. The mounting portion has a circular shape in transverse cross section, while the reference-surface portion has a square or rectangular shape in transverse cross section. The reference-surface portion has mutually perpendicular two vertically extending reference side surfaces which are parallel to the centerline of the mounting portion and which are made parallel to the X-axis and Y-axis directions when the angular position of each component camera <b>350</b>, <b>352</b> is adjusted as described below.

The adjusting jig is mounted on the nozzle holder <b>192</b> of the rotary nozzle holder <b>186</b>, such that the adjusting jig is rotatable relative to the nozzle holder <b>192</b>. The adjusting jig is moved to the component mounting position <b>130</b>F by rotation of the indexing disk <b>120</b>. At the component mounting position <b>130</b>F, the adjusting jig is rotated about its axis to an angular position in which the two side surfaces of the adjusting jig are parallel to the X-axis and Y-axis directions, respectively. To confirm the parallelism of the side surfaces to the X-axis and Y-axis directions, a dial indicator is fixed on the Y-axis slide <b>82</b> such that the plunger of the dial indicator is held in contact with the side surface of the adjusting jig substantially parallel to the Y-axis direction, for instance. The parallelism can be confirmed by reading the dial indicator while the Y-axis slide <b>82</b> is moved in the Y-axis direction. If the reading of the dial indicator whose plunger is held in contact with the above-indicated side surface remains constant when the Y-axis slide <b>82</b> is moved in the Y-axis direction, this means that the above-indicated side surface is parallel to the Y-axis direction.

After the angular position of the adjusting jig is adjusted such that the two side surfaces of the adjusting jig are parallel to the respective X-axis and Y-axis directions, the component-holding head <b>130</b> with the adjusting jig mounted on the rotary nozzle holder <b>186</b> is moved to the component hold-position detecting position <b>130</b>D. At this position, front images of the reference-surface portion of the adjusting jig are taken by the component cameras <b>350</b>, <b>352</b>, and image data representative of the front images are processed to calculate the positioning errors of the angular position of the imaging areas of the cameras <b>350</b>, <b>352</b> with respect to the reference-surface portion of the adjusting jig. The calculated angular positioning errors are indicated on a display device, so that the operator of the mounting system <b>12</b> can adjust the angular positions of the component cameras <b>350</b>, <b>352</b>, while observing the indicated angular positioning errors, so as to zero the angular positioning errors.

The adjustments of the XY positions and the angular position of the component cameras <b>350</b>, <b>352</b> are affected while the mounting system <b>12</b> is not in the component mounting operation, for instance, during manufacture, maintenance inspection or daily pre-operation inspection of the mounting system <b>12</b>. In the present embodiment, the detection of the positioning error of the head axis and other positioning errors and the adjustment of the angular positions of the component cameras <b>350</b>, <b>352</b> are affected during the daily pre-operation inspection of the mounting system <b>12</b>, so that the centers of the imaging areas of the component cameras <b>350</b>, <b>352</b> are aligned with the rotation axis of the reference suction nozzle before the component mounting operation is initiated.

Like the axis of rotation of the reference suction nozzle <b>190</b>, the axes of rotation of the suction nozzles <b>190</b> other than the reference suction nozzle <b>190</b> are detected on the basis of images of the sucking surfaces <b>201</b> of those other suction nozzles <b>190</b>, which are taken by the component cameras <b>350</b>, <b>352</b> whose positions have been adjusted as described above. The positioning errors of the rotation axes of the other suction nozzles <b>190</b> (hereinafter referred to as “ordinary suction nozzles <b>190</b>”) with respect to the rotation axis A of the reference suction nozzle <b>190</b> are obtained.

Each of the ordinary suction nozzles <b>190</b> is placed in its operating position, and two front images of the sucking surface <b>201</b> of each ordinary suction nozzle <b>190</b> are taken by each of the component cameras <b>350</b>, <b>352</b> at respective two different angular positions of the relevant component-holding head <b>130</b>. The two angular positions consist of the component-receiving angular position, and an angular position which is angularly spaced 180° from the component-receiving angular position. The midpoint between the center points of the two front images of the sucking surface <b>201</b> taken at the two angular positions is determined as the position of the axis of rotation of each ordinary suction nozzle <b>190</b>, and the positioning error of the thus determined axis of rotation of each ordinary suction nozzle <b>190</b> with respect to the center of the imaging area <b>38</b>B of each component camera <b>350</b>, <b>352</b> is obtained. Since the center of the imaging area <b>38</b>B of each component camera <b>350</b>, <b>352</b> has been aligned with the axis of rotation of the reference suction nozzle, the positioning error of the rotation axis A of each ordinary suction nozzle <b>190</b> with respect to the center of the imaging area <b>38</b>B represents the positioning error of the rotation axis of each ordinary suction nozzle with respect to the rotation axis of the reference suction nozzle.

In the present embodiment, the two images of each of the presently selected ordinary suction nozzles <b>190</b> in the operated position on all of the 16 component-holding heads <b>130</b> are taken at the respective two angular positions of each head <b>130</b>. Then, another ordinary suction nozzle <b>190</b> of each head <b>130</b> is placed in the operated position, and the two images of this ordinary suction nozzle <b>190</b> of each head <b>130</b> are taken at the respective two angular positions. Similar imaging operations are repeated until the two images of each of all ordinary suction nozzles <b>190</b> have been taken at the respective two angular positions.

Initially, the ordinary suction nozzles <b>190</b> held by the #1 nozzle holders <b>192</b> (except the #1 nozzle holder <b>192</b> holding the reference suction nozzle <b>190</b>) of the component-holding heads <b>130</b> are sequentially moved to the component hold-position detecting position <b>130</b>D, and the image of the sucking surface <b>201</b> of each ordinary suction nozzle <b>190</b> is taken in the upward direction by each component camera <b>350</b>, <b>352</b> while each head <b>130</b> is placed in its first imaging angular position, namely, in the component-receiving angular position. The head <b>130</b> holding the ordinary suction nozzle <b>190</b> whose image has been taken is moved to the angular-head-position resetting position <b>130</b>G, at which the head <b>130</b> is rotated by 180° by the angular-head-position resetting device <b>300</b>. The same head <b>130</b> is moved again to the component hold-position detecting position <b>130</b>D, at which the image of the sucking surface <b>201</b> is again taken while the head <b>130</b> is placed in its second imaging angular position which is 180° spaced from the first imaging angular position. The second engaging member <b>304</b> of the angular-head-position resetting device <b>300</b> is engageable with the first engaging member <b>174</b>, at two angular positions 180°-spaced from each other, namely, at the angular zero position or the angular position 180°-spaced from this angular zero position, so that the component-holding head <b>130</b> placed in the component-receiving angular position or the angular position 180°-spaced from this component-receiving angular position can be rotated by the angular-head-position resetting device <b>300</b>.

After the second image of the sucking surface <b>201</b> is taken at the second imaging angular position of the component-holding head <b>130</b>, the head <b>130</b> is moved again to the angular-head-position resetting position <b>130</b>G, at which the head <b>130</b> is rotated by 180° to the component-receiving angular position (first imaging angular position). The head <b>130</b> is then moved to the nozzle-holder selecting position <b>130</b>J, at which the rotary nozzle holder <b>186</b> is rotated by the nozzle-holder selecting device, to place the ordinary suction nozzle <b>190</b> held by the #2 nozzle holder <b>192</b> in the operating position, and the two images of the sucking surface <b>201</b> of this ordinary suction nozzle <b>190</b> are taken in the same manner as described above. The ordinary suction nozzles <b>190</b> of each head <b>130</b> are selectively placed in their operating position while the head <b>130</b> is placed in its component-receiving angular position <b>130</b>H, so that the first image of each ordinary suction nozzle <b>190</b> is taken at the component-receiving angular position <b>130</b>H of the corresponding head <b>130</b>. This is also true for the reference suction nozzle <b>190</b>. The same imaging operations are performed for all of the ordinary suction nozzles <b>190</b> of all of the component-holding heads <b>130</b>, to take the two images of the sucking surface <b>201</b> of each ordinary suction nozzle <b>190</b> at the respective two angular positions, and the position of the axis of rotation of each ordinary suction nozzle <b>190</b> is detected.

After the positions of the rotation axes of the ordinary suction nozzles <b>190</b> have been detected, the positioning errors of the rotation axes of the ordinary suction nozzles <b>190</b> with respect to the center of the imaging area <b>38</b>B of each component camera <b>350</b>, <b>352</b> are obtained, in the same manner as the positioning errors of the rotation axis Aref of the reference suction nozzle <b>190</b> with respect to the center of the imaging area <b>38</b>B. The thus obtained positioning errors of the rotation axes of the ordinary suction nozzles <b>190</b> with respect to the center of the imaging area <b>38</b>B of each component camera <b>350</b>, <b>352</b> represent the positioning errors of the rotation axes of the ordinary suction nozzles with respect to the rotation axis Aref of the reference suction nozzle. The obtained positioning error of the rotation axis of each ordinary suction nozzle are stored in the RAM <b>406</b>, together with the code data of the corresponding head <b>130</b>, the code data of the corresponding nozzle holder <b>192</b> and the data identifying the component camera <b>350</b>, <b>352</b>. The positioning error of the rotation axis Aord of each ordinary suction nozzle <b>190</b> is represented by error distances ΔXA and ΔYA, like the positioning error of the rotation axis A of the reference suction nozzle. As described above, the electronic component <b>38</b> is rotated for compensation for the angular positioning error Δθ when the electronic component <b>38</b> is mounted on the printed-wiring board <b>60</b>. The positioning error of the sucking position <b>38</b>A of the electronic component <b>38</b> due to this rotation for compensation for the angular positioning error Δθ is calculated on the basis of the axis of rotation of each suction nozzle which is obtained as described above. To calculate this center of the sucking position <b>38</b>A of the electronic component <b>38</b>, the position of the axis of rotation Aord of each ordinary suction nozzle <b>190</b> is calculated on the basis of the axis of rotation Aref of the reference suction nozzle and the positioning error of the axis of rotation Aord of each ordinary suction nozzle with respect to the axis of rotation Aref.

There will be described the manner of detecting the positioning error of the sucking surface <b>201</b> of each suction nozzle <b>190</b>. If the suction nozzle <b>190</b> is eccentric or bent relative to the nozzle body <b>198</b>, the position of the image of the sucking surface <b>201</b> is offset from the rotation axis A of the suction nozzle <b>190</b>, as indicated in FIG. <b>11</b>. Error distances ΔXN and ΔYN between the image of the sucking surface <b>201</b> and the rotation axis A represent an amount and a direction of a positioning error of the sucking surface <b>201</b> with respect to the rotation axis A (hereinafter referred to simply as “positioning error of the sucking surface <b>201</b>” where appropriate). In the present embodiment, the positioning error values ΔXN and ΔYN of the sucking surface <b>201</b> are obtained on the basis of the image of the sucking surface <b>201</b> taken at the component-receiving angular position <b>130</b>H of the corresponding component-holding head <b>130</b>, and the rotation axis A of the corresponding suction nozzle <b>190</b>. This manner of obtaining the positioning error values ΔXN and ΔYN is applicable to both the ordinary suction nozzles <b>190</b> and the reference suction nozzle <b>190</b>. The image of the sucking surface <b>201</b> used to obtain the positioning error of the sucking surface <b>201</b> is taken by one of the two component cameras <b>350</b>, <b>352</b>, for instance, by one of the cameras <b>350</b>, <b>352</b> which has a high magnification ratio. The amount and direction of the positioning error of the sucking surface <b>201</b> of each suction nozzle <b>190</b> are stored in the RAM <b>406</b>, together with the code data of the corresponding component-holding head <b>130</b> and nozzle holder <b>192</b>.

Where the electronic component <b>38</b> is the ordinary electronic component whose predetermined sucking position <b>38</b>A of the electronic component <b>38</b> is aligned with its center position, the component supply table <b>30</b>, <b>32</b> is moved so that the center position of the electronic component <b>38</b> to be transferred to the suction head <b>190</b> is aligned with the axis of rotation of the component-holding head <b>130</b> located at the component receiving position <b>130</b>A. In the presence of any of the positioning error of the tape feeder <b>36</b>, the positioning error of the rotation axis of the component-holding head <b>130</b> and the positioning error of the sucking surface <b>201</b> of the suction nozzle <b>190</b> with respect to the rotation axis of the head <b>130</b>, however, the center position of the ordinary electronic component <b>38</b> is offset from the rotation axis of the suction nozzle <b>190</b>, so that the center position of the electronic component <b>38</b> is not aligned with the sucking surface <b>201</b>. Where the predetermined sucking position <b>38</b>A of the electronic component <b>38</b> is offset from its center position, the sucking position <b>38</b>A of the electronic component <b>38</b> is not aligned with the sucking surface <b>201</b>. In view of the above aspects, the movement data for the component supply table <b>30</b>, <b>32</b> are prepared and modified on the basis of the predetermined sucking position <b>38</b>A of the electronic component <b>38</b> and the positioning errors described above, so that the electronic component <b>38</b> is sucked by the suction nozzle <b>190</b> without a misalignment of the sucking surface <b>201</b> with respect to the predetermined sucking position <b>38</b>A of the electronic component <b>38</b>.

The movement data used to move the component supply table <b>30</b>, <b>32</b> are modified on the basis of the X-axis components ΔXA and ΔXN of the positioning error values ΔXA and ΔYA of the rotation axis A of the suction nozzle <b>190</b> and the positioning error values ΔXN and ΔYA of the sucking surface <b>201</b>, which are detected as described above. Since the component supply table <b>30</b>, <b>32</b> is moved in the X-axis direction only, the movement data of the table <b>30</b>, <b>32</b> are adjusted for compensation for only the X-axis components ΔXA and ΔXN of those positioning error values ΔXA, ΔYA, ΔXN and ΔYN of the positioning error values. The table positioning device <b>46</b> is operated according to the thus modified or adjusted movement data, to move the component supply table <b>30</b>, <b>32</b>. The X-axis components ΔXA and ΔXN of the positioning error values are obtained on the basis of the image of the sucking surface <b>201</b> by the component camera <b>350</b>, <b>352</b>, and the obtained X-axis components ΔXA and ΔXN are adjusted for compensation for the positional difference between the component receiving position <b>130</b>A and the component hold-position detecting position <b>130</b>D, and for the reversal in the Y-axis direction of the image of the sucking surface taken by the component camera <b>350</b>, <b>352</b> in the upward direction. In this respect, it is noted that the X-axis components ΔXA and ΔXN of the positioning error values as indicated in FIGS. 12A, <b>12</b>B and <b>14</b> are the values after the adjustment for compensation for the positional difference and the image reversal. The rotation axis A of the suction nozzle <b>190</b> is detected for each of the two component cameras <b>350</b>, <b>352</b>, on the basis of the images of the sucking surface <b>201</b> taken by the two component cameras <b>350</b>, <b>352</b>. However, the positioning error of the sucking surface <b>201</b> used to modify the movement data of the component supply table <b>30</b>, <b>32</b> is detected on the image of the sucking surface <b>201</b> taken by one of the two component cameras <b>350</b>, <b>352</b>, for instance, by the camera <b>350</b>, <b>352</b> which has the higher magnification ratio. The position of the rotation axis Aord of each ordinary suction nozzle <b>190</b> may also be detected on the basis of the image taken by one of the two component cameras <b>350</b>, <b>352</b>, for example, by the camera having the higher magnification ratio. The position of the rotation axis Aord of each ordinary suction nozzle is obtained on the basis of the rotation axis Aref of the reference suction nozzle and the positioning error of the rotation axis Aord of the ordinary suction nozzle with respect to the rotation axis Aref of the reference suction nozzle. The positioning error value of the rotation axis Aord of the ordinary suction nozzle obtained on the basis of the image taken by the camera <b>350</b> is the same as that obtained on the basis of the image taken by the camera <b>352</b>.

FIG. 12A indicates an error distance ΔXB of the sucking position <b>38</b>A of the electronic component <b>38</b> with respect to its center position, an error distance ΔXA of the rotation axis Aord of the ordinary suction nozzle <b>190</b> with respect to that of the reference suction nozzle, and an error distance ΔXN of the rotation axis Aord of the ordinary suction nozzle with respect to the center <b>201</b>A of the sucking surface <b>201</b>. On the basis of these error distances, the movement data of the component supply device <b>30</b>, <b>32</b> are prepared and modified. In FIGS. 12A and 12B, an arrow T indicates the direction of movement of the component supply table <b>30</b>, <b>32</b> when the electronic component <b>38</b> is received by the suction nozzle <b>190</b>, and arrows of the lines representing the error distances are directions in which the component supply table <b>30</b>, <b>32</b> is moved for compensation for the error distances.

The movement data of the component supply tables <b>30</b>, <b>32</b> are prepared such that the predetermined sucking position <b>38</b>A of the electronic component <b>38</b> is aligned with the axis of rotation of the reference suction nozzle, and the thus prepared movement data are modified on the basis of the positioning error values ΔXA and ΔXN. The movement data for the component supply table <b>30</b>, <b>32</b> are prepared on the basis of the position of the component supply table <b>30</b>, <b>32</b> and the predetermined sucking portion (defined by the offset distance ΔXB) when the center position of the ordinary electronic component <b>38</b> is aligned with the rotation axis A of the reference suction nozzle <b>190</b> in the X-axis direction while at the same time the widthwise center <b>38</b>C of the opening <b>26</b> is aligned with the rotation axis A of the reference suction nozzle <b>190</b>. Since the positioning error of the tape feeder <b>36</b> is not obtained upon a daily pre-operation inspection of the mounting system <b>12</b>, the positioning error of the tape feeder <b>36</b> is not taken into account when the movement data are prepared. The movement data of the component supply tables <b>30</b>, <b>32</b> are prepared and modified for all the tape feeders <b>36</b> from which the electronic components <b>38</b> are supplied. Each of the component-holding heads <b>130</b> are rotated to their angular zero position (component-receiving angular position <b>130</b>H) when the heads <b>130</b> are located at the angular-head-position resetting position <b>130</b>G after the electronic components <b>38</b> have been mounted on the printed-wiring board <b>12</b>. Accordingly, each component-holding head <b>130</b> receives the electronic component <b>38</b> when the head <b>130</b> is placed in the predetermined component-receiving angular position <b>130</b>H. The positioning error of the suction pipe <b>200</b> with respect to the tape feeder <b>36</b> due to the positioning error of the sucking surface <b>201</b> with respect to the rotation axis A of the suction nozzle <b>190</b> is the same for each of the component-holding heads <b>130</b>, for each of the electronic components <b>38</b> to be supplied from that tape feeder <b>36</b>. Further, the individual suction nozzles <b>190</b> have respective positioning errors of their rotation axes. The same positioning error is used to modify the movement data of the component supply table <b>30</b>, <b>32</b> for the same suction nozzle <b>190</b> which receives the electronic components <b>38</b> from the same tape feeder <b>36</b>. The movement data of the component supply table <b>30</b>, <b>32</b> are modified such that the predetermined sucking position <b>38</b>A of the electronic component <b>38</b> is substantially aligned with the center position of the sucking surface <b>201</b> in the X-axis direction, as indicated in FIG. 12B, so that the electronic component <b>3</b> can be held by the suction nozzle <b>190</b> with high stability, even where the electronic component <b>38</b> is comparatively large while the positioning error of the sucking surface <b>201</b> is comparatively large. Although FIG. 12B shows that the sucking position <b>38</b>A of the electronic component <b>38</b> is aligned with the center position of the sucking surface <b>201</b> in the Y-axis direction, too, they are not actually aligned with each other since the movement data are not modified for compensation for the positioning error in the Y-axis direction. Thus, the movement data for the ordinary suction nozzles <b>190</b> are prepared and modified for alignment of the predetermined sucking position <b>38</b>A of the electric component <b>38</b> with the center position of the sucking surface <b>201</b>. The movement data for the reference suction nozzle <b>190</b> are prepared in the same manner as that for the ordinary suction nozzles <b>190</b>, except that the positioning error value ΔXA is zeroed, so that the electronic component <b>38</b> is sucked by the reference suction nozzle with a reduced amount of error of the sucking position <b>38</b>A. The movement data for the ordinary electronic component <b>38</b> are prepared with the positioning error value ΔXB being zeroed. Thus, the movement data for the component supply table <b>30</b>, <b>32</b> are prepared depending upon whether the electronic component <b>38</b> is the ordinary component having a rectangular shape or a non-ordinary component, and depending upon whether the suction nozzle <b>190</b> is the reference suction nozzle or the ordinary suction nozzle.

There will be described the manner of detecting the positioning error of the tape feeder <b>36</b> and the manner of modifying the movement data for compensation for the detected positioning error. In the present embodiment, the positioning error of the tape feeder <b>36</b> is detected when the electronic component <b>38</b> is mounted on the printed-wiring board <b>60</b>. Even when the movement data of the component supply table <b>30</b>, <b>32</b> are prepared and modified on the basis of the predetermined sucking position <b>38</b>A of the electronic component <b>38</b> and the positioning errors described above, the electronic component <b>38</b> held by the suction nozzle <b>190</b> may still have a positioning error in the X-axis direction, namely, the predetermined sucking position <b>38</b>A of the electronic component <b>38</b> may not be aligned with the center position of the sucking surface <b>201</b>. This misalignment may be caused by a positioning error of the tape feeder <b>36</b>. The positioning error of the tape feeder <b>136</b> in the X-axis direction is obtained on the basis of the horizontal positioning error ΔXE obtained on the basis of the image of the electronic component <b>38</b> held by the suction nozzle <b>190</b>.

Where the horizontal positioning error ΔXE of the electronic component <b>38</b> is detected, as indicated in FIG. 13, X-axis error of the center position of the sucking surface <b>201</b> with respect to the center of the imaging area <b>38</b>B is subtracted the horizontal positioning error ΔXE, and the thus obtained difference is stored in the RAM <b>406</b>, as the positioning error of the tape feeder <b>36</b> in the X-axis direction, together with data identifying the tape feeder <b>36</b> from which the component <b>38</b> is supplied. The horizontal positioning errors ΔXE and ΔYE are error distances between the predetermined sucking position <b>38</b>A of the electronic component <b>38</b> and the center of the imaging area <b>38</b>B. If the predetermined sucking position <b>38</b>A lies on the center of the electronic component <b>38</b>, the horizontal positioning errors ΔXE and ΔYE are error distances between the center of the electronic component <b>38</b> and the center of the imaging area <b>38</b>B. The center position of the sucking surface <b>201</b> in the imaging area is obtained on the basis of the positioning error of the sucking surface <b>201</b>, where the suction nozzle <b>190</b> is the reference suction nozzle. Where the suction nozzle <b>190</b> is one of the ordinary suction nozzles, the center position of the sucking surface <b>201</b> is obtained on the basis of the positioning error of the rotation axis of the ordinary suction nozzle with respect to that of the reference suction nozzle, and the positioning error of the sucking surface <b>201</b>. Where the angular position of the electronic component <b>38</b> is changed, the positioning error of the tape feeder <b>36</b> is obtained on the basis of a change of the angular position of the electronic component <b>38</b>. Namely, a positioning error of the center <b>201</b>A of the sucking surface <b>201</b> with respect to the predetermined sucking position <b>38</b>A of the electronic component <b>38</b> before the suction nozzle <b>190</b> is rotated to change the angular position of the electronic component <b>38</b> is obtained on the basis of the obtained image data, that is, the predetermined sucking position <b>38</b>A of the electronic component <b>38</b>, the center position of the sucking surface <b>201</b>, the position of the axis of rotation A of the suction nozzle <b>190</b> and the angle and direction of rotation of the suction nozzle <b>190</b> to change the angular position of the electronic component <b>38</b> . When a predetermined number of the electronic components <b>38</b> have been supplied from the same tape feeder <b>36</b>, an average of the X-axis positioning error values obtained of those electronic components <b>38</b> is calculated, and is used as a positioning error ΔXF of that tape feeder <b>36</b> in the X-axis direction. The position error values ΔXF of all the tape feeders <b>36</b> are stored in the RAM <b>406</b>, together with data indicative of the X-axis positions of the tape feeders <b>36</b> on the feeder support block <b>34</b>. Although FIG. 13 shows the electronic component <b>38</b> as viewed in the downward direction, for easier understanding, the image of the electronic component <b>38</b> is actually formed in the imaging area such that the image is reversed in the Y-axis direction.

The movement data for the component supply table <b>30</b>, <b>32</b> are modified on the basis of the positioning error ΔXF of each tape feeder <b>36</b>. Where the positioning error ΔXF of the tape feeder <b>36</b> is detected, for instance, the movement data are modified for compensation for the positioning error ΔXF of the tape feeder <b>36</b> as well as the positioning error ΔXA of the rotation axis of the suction nozzle and other positioning errors, so that the electronic component <b>38</b> can be held by the suction nozzle <b>190</b> with increased stability. This modification is also affected while taking into account the positional difference between the component-receiving position and the component hold-position detecting position <b>130</b>D and the Y-axis reversal of the image of the electronic component <b>38</b> taken by the component camera <b>350</b>, <b>352</b> in the upward direction.

The detection of the positioning error of the tape feeder <b>36</b> and the modification of the movement data of the component supply table <b>30</b>, <b>32</b> are affected during the component mounting operation. The detection and modification may be affected either once during the mounting operation of a selected one of the electronic components <b>38</b> supplied form each tape feeder <b>36</b>, or for all of those electronic components <b>38</b>. Alternatively, the detection and modification are affected when a predetermined condition is satisfied, for instance, when a predetermined number of the electronic components <b>38</b> have been supplied from the relevant tape feeder <b>36</b>. In this case, the number of the electronic components <b>38</b> supplied from the tape feeder <b>36</b> is counted during the component mounting operation and compared with the predetermined number. This predetermined number is determined to be larger than the predetermined number used to obtain the positioning error ΔXF indicated above. Where the detection of the positioning error of the tape feeder <b>36</b> is affected two or more times, the movement data of the component supply table <b>30</b>, <b>32</b> are updated each time the positioning error is detected.

When the predetermined condition for detecting the positioning error of the tape feeder <b>36</b> is satisfied after the initiation of the component mounting operation, for example, when a predetermined time has passed after the initiation of the component mounting operation, the component mounting operation is interrupted, and the positioning error is detected to modify the movement data. In the present embodiment, the positioning error of the rotation axis Aref of the reference suction nozzle and the positioning error of the sucking surface <b>201</b> are also detected when the positioning error of the tape feeder <b>36</b> is detected. However, the positioning error of the rotation axis A of the ordinary suction nozzle <b>190</b> is not detected at this time, but the positioning error of the same detected when the mounting system <b>12</b> is not in operation is used to modify the movement data.

The rotation axis Aref of the reference suction nozzle <b>190</b> is detected on the basis of the two images of the sucking surface <b>201</b> of the reference suction nozzle <b>190</b>, and the positioning errors of the center points of the imaging areas of the component cameras <b>350</b>, <b>352</b> with respect to the detected rotation axis Aref of the reference suction nozzle <b>190</b> are obtained. However, the positions of the component cameras <b>350</b>, <b>352</b> are not actually adjusted during the component mounting operation, but the movement data of the board positioning device <b>64</b> are modified for compensation for the obtained positioning errors of the cameras <b>350</b>, <b>352</b>. Namely, the obtained positioning errors of the center points of the imaging areas with respect to the rotation axis Aref of the reference suction nozzle <b>190</b> are stored in the RAM <b>406</b>, and the horizontal positioning errors of the electronic component <b>38</b> with respect to the rotation axis Aref of the reference suction nozzle are obtained on the basis of the stored positioning errors, so that the movement data of the board positioning device <b>64</b> are modified on the basis of the obtained horizontal positioning errors. To detect the center position error of the electronic component <b>38</b> due to the angular position adjustment for compensation for the angular positioning errorΔθ, the position of the rotation axis A of the ordinary suction nozzle <b>190</b> is obtained on the basis of the positioning error of the center of the imaging area <b>38</b>B, and the positioning error of the rotation axis A of the ordinary suction nozzle with respect to the rotation axis Aref of the reference suction nozzle. The positioning error of the sucking surface <b>201</b> of the reference suction nozzle <b>190</b> is detected on the basis of the image of the sucking surface <b>201</b> taken when the component-holding head <b>130</b> is placed in the angular zero position or component-receiving angular position. The positioning error of the sucking surface <b>201</b> of the ordinary suction nozzle <b>190</b> with respect to its rotation axis A is detected on the basis of the image of the sucking surface <b>201</b> taken when the head <b>130</b> is placed in the angular zero position. At this time, too, the position of the rotation axis A of the ordinary suction nozzle <b>190</b> is obtained on the basis of the positioning error of the center of the imaging area <b>38</b>B, and the positioning error of the rotation axis A of the ordinary suction nozzle with respect to the rotation axis Aref of the reference suction nozzle.

When the suction nozzle <b>190</b> is changed from one to another, the positioning errors such as the positioning error of the rotation axis A of the component-holding head <b>130</b> are detected, and the movement data of the component supply table <b>30</b>, <b>32</b> are modified according to the detected positioning errors. In this case, the position of the rotation axis A of at least the presently selected suction nozzle <b>190</b> is detected. However, the positions of the rotation axes of the other suction nozzles <b>190</b> may be detected. When the reference suction nozzle <b>190</b> is changed to one of the ordinary suction nozzles <b>190</b>, the positions of the rotation axes of all the suction nozzles <b>190</b> including the new reference suction nozzle are detected, and the positioning errors of the rotation axes of the ordinary suction nozzles with respect to the rotation axis A of the reference suction nozzle are detected. In this case, the actual positions of the component cameras <b>350</b>, <b>352</b> are not adjusted, but the movement data of the board positioning device <b>64</b> are modified for compensation for the positioning errors of the center positions of the imaging areas of the cameras <b>350</b>, <b>352</b>.

It will be understood from the foregoing description of the present embodiment that a relative-position obtaining portion operable to obtain a relative position between the sucking surface <b>201</b> of the suction nozzle <b>190</b> and the rotation axis of the component-holding head <b>130</b> placed in a predetermined angular position is constituted by a portion of the control device <b>400</b> assigned to rotate the component-holding head <b>130</b> to two imaging angular positions, operate the component cameras <b>350</b>, <b>352</b> to take images of the sucking surface <b>201</b> at the two imaging angular positions, and detect the positioning error of the sucking surface <b>201</b> with respect to the rotation axis of the head <b>130</b> in the component-receiving angular position. It will also be understood that a relative-movement control portion operable to control the table positioning devices <b>46</b> for moving the component-holding head <b>130</b> and the component supply device <b>14</b> relative to each other is constituted by a portion of the control device <b>400</b> assigned to prepare and modify the movement data of the component supply tables <b>30</b>, <b>32</b> on the basis of the predetermined sucking position <b>38</b>A of the electronic component <b>38</b>, the detected positioning error of the sucking surface <b>201</b>, the detected positioning error of the rotation axis of the head <b>130</b> and the detected positioning error of the tape feeder <b>36</b>, and to control the table positioning devices <b>46</b> according to the modified movement data, for moving the component supply tables <b>30</b>, <b>32</b>. It will further be understood that a component-transfer control portion operable to move the component-holding head <b>130</b> and the component supply device <b>14</b> toward each other, for transferring the electronic component <b>38</b> from the component supply device <b>14</b> to the suction nozzle <b>190</b> is constituted by a portion of the control device <b>400</b> assigned to rotate the component-holding head <b>130</b> to the angular zero position and operate the head lifting and lowering device <b>230</b> for lowering the component-holding head <b>130</b> toward the component supply device <b>14</b>, for the suction nozzle <b>190</b> to receive the electronic component <b>38</b>.

The component mounting operation may be interrupted to detect the position of the rotation axis A of the ordinary suction nozzle <b>190</b> and obtain the positioning error of the rotation axis A of the ordinary suction nozzle with respect to the rotation axis A of the reference suction nozzle. In this case, the component-holding head <b>130</b> is rotated to the two imaging angular positions, for taking the two images of the sucking surface <b>201</b> when the head <b>130</b> is placed in the respective two imaging angular positions.

While each component-holding head <b>130</b> in the first embodiment is turned by the turning device <b>132</b> about the vertical axis, a component-holding head may be moved by a suitable XY positioning device in mutually perpendicular X-axis and Y-axis directions in an XY plane parallel to the surface of the printed-wiring board. An electronic-component mounting system having such component-holding head and XY positioning device according to a second embodiment of this invention will be briefly described by reference to FIGS. 15-18. An example of this type of electronic-component mounting system is disclosed in JP-B2-2824378.

Referring first to FIG. 15, reference numeral <b>600</b> denotes a machine base of an electronic-component mounting system <b>601</b>. The electronic-component mounting system includes a printed-wiring board conveyor (PWB conveyor) <b>604</b>, a component mounting device <b>608</b>, component supply devices <b>610</b>, <b>612</b>, and a printed-wiring board support device (PWB support device) <b>616</b>, which are mounted on the machine base <b>600</b>. The PWB conveyor <b>604</b> is arranged to transfer a circuit substrate in the form of a printed-wiring board <b>602</b> in an X-axis direction (in the left and right directions as seen in FIG. <b>15</b>). The component mounting device <b>608</b> is arranged to mount electric components in the form of electronic components <b>606</b> (FIG. 18) on the printed-wiring board <b>602</b>. The component supply devices <b>610</b>, <b>612</b> are arranged to supply the component mounting device <b>608</b> with the electronic components <b>506</b>. The PWB support device <b>616</b>, which serves as a circuit-substrate support device, is arranged to support the printed-wiring board <b>602</b>.

In the present second embodiment, the printed-wiring board <b>602</b> is transferred by the PWB conveyor <b>604</b> such that the printed-wiring board <b>602</b> maintains a horizontal attitude or posture. The PWB conveyor <b>604</b> is stopped by a suitable stopper device (not shown), to locate the board <b>602</b> at a predetermined component-mounting position. The board <b>602</b> located at the component-mounting position is supported by the PWB support device <b>616</b>. In the present electronic-component mounting system <b>601</b>, the printed-wiring board <b>602</b> is supported such that a component-mounting surface <b>618</b> of the board <b>602</b> on which the electronic components <b>606</b> are mounted is parallel to the horizontal plane, as indicated in FIG. <b>18</b>.

In the present embodiment, too, movement data for moving and positioning a component-holding head <b>690</b> (which will be described) of the component mounting device <b>608</b> are defined in an XY coordinate system in which the electronic component <b>606</b> is seen in the downward direction (Z-axis direction) and in which the above-indicated X-axis direction and a Y-axis direction are respectively parallel to the horizontal and vertical directions as seen in the plan view of FIG. 15 wherein the component supply device <b>612</b> is located above the component supply device <b>610</b>. The upward and rightward directions in FIG. 15 are positive X-axis and Y-axis directions, respectively.

The component supply devices <b>610</b>, <b>612</b> are spaced from each other in the Y-axis direction of the XY coordinate system, and located on the opposite sides of the PWB conveyor <b>604</b>, as shown in FIGS. 15 and 16. In the present embodiment, the component supply device <b>610</b> is of tape feeder type, while the component supply device <b>612</b> is of tray type.

The component supply device <b>610</b> of tape feeder type includes a component supply table <b>664</b> on which a multiplicity tape feeders <b>660</b> are mounted such that the component-supply portions of the tape feeders <b>660</b> are arranged in a straight line parallel to the X-axis direction. Like the tape feeder <b>36</b> described above, each tape feeder <b>660</b> has a tape cartridge arranged to feed a carrier tape which accommodates the electronic components <b>606</b>.

The component supply device <b>612</b> of tray type includes a multiplicity of component trays <b>666</b> (FIG. 18) each accommodating a multiplicity of electronic components <b>606</b>. The component trays <b>666</b> are accommodated in respective multiple tray boxes <b>668</b>, which are vertically arranged and are supported by respective support members. The tray boxes <b>668</b> are elevated one after another by an elevator device disposed within a column <b>670</b> (FIG. <b>15</b>), to a predetermined component-supply position. For the component-holding head <b>690</b> (which will be described) of the component mounting device <b>608</b> to receive the electronic components <b>606</b> from the component tray <b>666</b> in the tray box <b>668</b> located at the component-supply position, some vertical space must be provided above the component-supply position. To provide this vertical space, the tray box <b>668</b> from which the electronic components <b>606</b> have been transferred to the component-holding head <b>690</b> is moved further upwards from the component-supply position to a predetermined retracted position when the next tray box <b>668</b> is moved to the component-supply position, so that the required vertical space is provided between the component-supply position and the retracted position. The component supply device <b>612</b> of tray type is identical in construction to a component supply device disclosed in JP-B2-2-57719.

The component-holding head <b>690</b> of the component mounting device <b>608</b> is movable in the mutually perpendicular X-axis and Y-axis directions, so that the component-holding head <b>690</b> can take a linear movement having X-axis and Y-axis components, to move each electronic component <b>606</b> to a desired position on or above the component-mounting surface <b>618</b> of the printed-wiring board <b>602</b>. To move the component-holding head <b>690</b> in the X-axis direction, the component mounting device <b>608</b> includes two ballscrews <b>694</b> disposed on the machine base <b>600</b>, on the opposite sides of the PWB conveyor <b>604</b>, so as to extend in the X-axis direction, as sown in FIG. 15, and an X-axis slide <b>696</b> having two ballnuts <b>698</b> (only one of which is shown in FIG. 17) which engage the respective ballscrews <b>694</b>. The device <b>608</b> further includes two X-axis drive motors <b>700</b> for rotating the ballscrews <b>694</b>, for moving the X-axis slide <b>696</b> in the X-axis direction.

As shown in FIG. 18, the X-axis slide <b>696</b> extends in the Y-axis direction across the PWB conveyor <b>604</b>, and has a length corresponding to the distance between the component supply device <b>610</b> of feeder type and the component supply device <b>612</b> of tray type. On the machine base <b>600</b>, there are disposed two guide rails <b>702</b> (FIG. 17) located under the respective ballscrews <b>694</b>. The X-axis slide <b>696</b> has two guide blocks <b>704</b> which slidably engage the guide rails <b>702</b>, for guiding the X-axis slide <b>696</b> in the X-axis direction. It will be understood that the ballscrews <b>694</b>, ballnuts <b>698</b> and X-axis drive motors <b>700</b> cooperate with each other to constitute an X-axis drive device <b>706</b>.

On the X-axis slide <b>696</b>, there is disposed a ballscrew <b>710</b> so as to extend in the Y-axis direction, as shown in FIG. <b>17</b>. The X-axis slide <b>696</b> carries a Y-axis slide <b>712</b> having a ballnut <b>714</b> which engages the ballscrew <b>710</b>. The ballscrew <b>710</b> is rotated by a Y-axis drive motor <b>716</b> (FIG. 15) through gears <b>718</b>, <b>720</b>, so that the Y-axis slide <b>712</b> is moved in the Y-axis direction while being guided by a pair of guide rails <b>722</b> (FIG. <b>17</b>). It will be understood that the ballscrew <b>710</b>, ballnut <b>714</b> and Y-axis drive motor <b>716</b> constitute a Y-axis drive device <b>724</b>, and that the Y-axis drive device <b>724</b> cooperates with the X-axis slide <b>696</b>, X-axis drive device <b>706</b> and Y-axis slide <b>712</b>, to constitute an XY positioning device <b>726</b> for moving the component-holding head <b>690</b> to a desired position in the XY plane.

The Y-axis slide <b>712</b> has a support portion <b>732</b> on which there are mounted the above-indicated component-holding head <b>690</b>, a Z-axis drive device <b>734</b> for moving up and down the component-holding head <b>690</b> in a Z-axis direction, and a rotary drive device <b>736</b> for rotating the component-holding head <b>690</b> about its axis. The component-holding head <b>690</b>, the Z-axis drive device <b>734</b> and the rotary drive device <b>736</b> constitute a component mounting unit <b>738</b>. Although the component mounting device <b>738</b> in the present electronic-component mounting system includes only one component mounting unit, the electronic-component mounting system may include a plurality of component mounting units. For instance, the two or more component mounting units are disposed on the Y-axis slide <b>712</b> such that the units are arranged in a row in the Y-axis direction.

The component mounting unit in the present embodiment is identical with a component mounting unit as disclosed in JP-B2-4-3093339. The component mounting unit will be described only briefly.

The support portion <b>732</b> supports a shaft <b>740</b> such that the shaft <b>740</b> is axially movable in the Z-axis direction and rotatable about its axis. The shaft <b>740</b> carries a nozzle holder <b>742</b> at its lower end. A suction nozzle <b>744</b> is removably held by the nozzle holder. In the present embodiment, the shaft <b>740</b> and the nozzle holder <b>742</b> cooperate to constitute the component-holding head <b>690</b>.

The Z-axis drive device <b>734</b> includes a drive source in the form of a Z-axis drive motor <b>750</b>, and a rotary motion of the Z-axis drive motor <b>750</b> is transmitted to a ballnut <b>756</b> through a rotary motion transmitting device including gears <b>752</b>, <b>754</b>. With a rotary motion of the ballnut <b>756</b>, the shaft <b>740</b> engaging the ballnut <b>756</b> is moved in the Z-axis direction to lift and lower the component-holding head <b>690</b>. The Z-axis drive device <b>734</b> functions as a device operable to move the component-holding head <b>690</b> toward and away from the printed-wiring board <b>602</b>. The rotary drive device <b>736</b> includes a drive source in the form of a nozzle rotation motor <b>760</b> (FIG. <b>19</b>), and a rotary motion of the nozzle rotation motor <b>760</b> is transmitted to the shaft <b>740</b> through a rotary motion transmitting device including a gear <b>762</b>. With a rotary motion of the shaft <b>740</b> about its axis, the component-holding head <b>690</b> is rotated about its vertically extending axis.

The suction nozzle <b>744</b> is arranged to hold each electronic component <b>606</b> by suction under a negative pressure, and mount the electronic component <b>606</b> on the printed-wiring board <b>602</b>. To this end, the suction nozzle <b>744</b> is connected through a solenoid-operated directional control valve device (not shown) to a negative pressure source, a positive pressure source and the atmosphere. With a switching operation of the directional control valve device, the suction nozzle <b>744</b> is selectively communicated with one of the negative and positive pressure sources and the atmosphere. The suction nozzle <b>744</b> has a sucking surface <b>772</b> which faces downwards and at which the electronic component <b>606</b> is sucked by suction.

The Y-axis slide <b>712</b> further carries a stationary image-taking device in the form of a fiducial mark camera <b>780</b> (FIGS. 15 and 18) operable to take an image of a fiducial mark <b>778</b> provided on the printed-wiring board <b>602</b>, as shown in FIG. <b>15</b>. In the present embodiment, the fiducial mark camera <b>780</b> is a CCD camera adapted to take a two-dimensional image at one time. An illuminating device <b>782</b> is provided to illuminate the fiducial mark <b>778</b> and its vicinity, when the image of the fiducial mark <b>778</b> is taken by the fiducial mark camera <b>780</b>.

On the X-axis slide <b>696</b>, there are fixedly disposed two image-taking devices <b>790</b> at respective two Y-axis positions corresponding to the respective two ballscrews <b>694</b> provided to move the X-axis slide <b>696</b>. One of the two image-taking devices <b>790</b> is located between the component supply device <b>610</b> of tape feeder type and the printed-wiring board <b>602</b>, while the other image-taking device <b>790</b> is located between the component supply device <b>612</b> of tray type and the board <b>602</b>. The two image-taking devices <b>790</b> are identical in construction with each other.

Each image-taking device <b>790</b> includes a component camera <b>792</b> for taking an image of the electronic component <b>606</b>, and a waveguide device <b>794</b>. The waveguide device <b>794</b> includes a reflecting device in the form of reflecting mirrors <b>796</b>, <b>798</b>, which are attached through respective brackets to the underside of the X-axis slide <b>696</b>. The reflecting mirror <b>796</b> is disposed at a position within a path of movement of the component-holding head <b>690</b> in the Y-axis direction, and has a reflecting surface <b>800</b> which is inclined about 45° with respect to a vertical plane including the centerline of the suction nozzle <b>744</b>, such that one of the opposite ends of the reflecting surface <b>800</b> (as viewed in the X-axis direction) which is closer to the X-axis slide <b>696</b> is the lower end, that is, the left end of the reflecting surface <b>800</b> is the lower end.

The other reflecting mirror <b>798</b> is disposed on the side of the X-axis slide <b>696</b> which is remote from the reflecting mirror <b>796</b> and has a reflecting surface <b>802</b> which is inclined with respect to the vertical plane, symmetrically with the reflecting mirror <b>800</b>. The component camera <b>792</b> for taking the image of the electronic component <b>606</b> held by the suction nozzle <b>744</b> is located on the side of the X-axis slide <b>696</b> remote from the component-holding head <b>690</b>, such that the component camera <b>792</b> faces downwards toward the reflecting surface <b>802</b> of the reflecting mirror <b>798</b>.

In this arrangement, the image of the electronic component <b>606</b> held by the suction nozzle <b>744</b> can be taken by the component camera <b>792</b> when the component-holding head <b>690</b> is moved by the XY positioning device <b>726</b> to the Y-axis position of the corresponding ballscrew <b>694</b> at which the electronic component <b>606</b> is located right above the reflecting mirror <b>800</b> and at which a visible light reflected by a light emitting plate <b>812</b> (which will be described) is reflected by the reflecting mirrors <b>796</b>, <b>798</b> and is incident upon the component camera <b>792</b>. Thus, the image-taking device <b>790</b> is arranged to image the electronic component <b>606</b> located at the predetermined image-taking position which lies within a path of movement of the electronic component <b>606</b> when the Y-axis slide <b>712</b> is moved in the Y-axis direction relative to the X-axis slide <b>696</b>. In the present embodiment, the component camera <b>792</b> is a two-dimensional CCD camera, like the fiducial mark camera <b>780</b> described above. The reflecting mirror <b>798</b> may be eliminated. In this case, the component camera <b>250</b> is disposed so as to have a horizontal attitude and face toward the reflecting mirror <b>796</b>.

A strobe light <b>810</b> as a UL irradiating device is disposed near the reflecting mirror <b>796</b>, for irradiating the light emitting plate <b>812</b> of the suction nozzle <b>744</b> with a ultraviolet radiation. The light emitting plate <b>812</b> absorbs the ultraviolet radiation, and emits the visible light for illuminating the bottom surface of the electronic component <b>606</b> held by the suction nozzle <b>744</b>. In the present embodiment, the light emitting plate <b>812</b> and the stroke light <b>810</b> provided as the UV irradiating device cooperate to constitute an illuminating device for the image-taking device <b>790</b>.

Another strobe light <b>814</b> for emitting a visible light is disposed nearer to the suction nozzle <b>744</b> than the above-indicated strobe light <b>810</b>. This strobe light <b>814</b> serves as an illuminating device for illuminating the bottom surface of the electronic component <b>606</b>, for taking a normal image of the electronic component <b>82</b> rather than a silhouette image. The bottom surface of the electronic component <b>606</b> is the surface at which the electronic component <b>606</b> is mounted on the printed-wiring board <b>602</b>. The image-taking devices <b>790</b> and the illuminating devices constitute an imaging system.

The present electronic-component mounting system <b>601</b> is provided with control means in the form of a control device <b>830</b> as shown in FIG. <b>19</b>. Like the control device <b>400</b> used in the first embodiment, the control device <b>830</b> is principally constituted by a computer <b>832</b>. The same reference signs as used in FIG. 8 are used in FIG. 19 to identify the functionally corresponding elements of the control device <b>830</b>, and redundant description of these elements will not be provided. In the present second embodiment, too, the X-axis drive motors <b>700</b> and other drive sources are servomotors, and operating amounts of these servomotors are detected by respective encoders, the output signals of which are fed to the computer <b>832</b>. In FIG. 19, an encoder <b>836</b> provided for the nozzle rotation motor <b>760</b> is shown by way of example. The RAM <b>406</b> is used to store various control programs down-loaded from a host computer. The control programs include a control program for executing a main control routine, a component-mounting control program, a control program for detecting the axis of rotation of the component-holding head <b>690</b>, and a control program for detecting the positioning error of the sucking surface <b>772</b> of the suction nozzle <b>744</b>. The RAM <b>406</b> also stores data necessary to execute the control programs.

An operation of the present electronic-component mounting system <b>601</b> will then be described. The operation to mount the electronic component <b>606</b> on the printed-wiring board <b>602</b> is described in JP-B2-2824378 and Japanese Patent Application No. 2000-343641 (not laid open at the time the present invention was made). The operation of the system <b>601</b> in general will be only briefly described, and those aspects of the operation which relate to the present invention will be described in detail.

When the electronic component <b>606</b> is mounted on the printed-wiring board <b>602</b>, the component-holding head <b>690</b> is moved by the X-axis slide <b>696</b> and the Y-axis slide <b>712</b>, to the component supply position at the component supply device <b>610</b> of tape feeder type or the component supply device <b>612</b> of tray type. The component-holding head <b>690</b> is vertically moved by the Z-axis drive device <b>734</b>, so that the suction nozzle <b>744</b> holds the electronic component <b>606</b> by suction under a negative pressure. At this time, the component-holding head <b>690</b> is placed in its predetermined component-receiving angular position for receiving the electronic component <b>606</b>. In the present embodiment, the component-receiving angular position of the component-holding head <b>690</b> is detected on the basis of the output signal of the encoder <b>836</b> provided to detect the operating amount of the nozzle rotation motor <b>760</b>. Each time the component-holding head <b>690</b> receives the electronic component <b>606</b>, the head <b>690</b> is rotated by the nozzle rotation motor <b>760</b> to its predetermined component-receiving angular position. There will be described an operation to be performed when the component-holding head <b>690</b> receives the electronic component <b>606</b> from one of the tape feeders <b>660</b> of the component supply device <b>610</b> of tape feeder type, by way of example.

The component-holding head <b>690</b> is moved from the component supply position at the tape feeder <b>660</b>, more particularly, from a predetermined component-receiving position at which the electronic component <b>606</b> is received from the tape feeder <b>660</b>, to the predetermined component-mounting position at which the electronic component <b>606</b> is mounted on the printed-wiring board <b>602</b>. At this time, the component-holding head <b>690</b> holding the electronic component <b>606</b> passes a position right above the reflecting mirror <b>796</b> of one of the two image-taking devices <b>790</b>, which reflecting mirror <b>796</b> is fixedly disposed at a position on the X-axis slide <b>696</b> between the component-receiving position at the tape feeder <b>660</b> and the component-mounting position. Described more specifically, when the component-holding head <b>690</b> is moved from the component supply position to the component-mounting position, the Y-axis slide <b>712</b> is necessarily moved on the X-axis slide <b>696</b> between the component supply device <b>610</b> of tape feeder type and the printed-wiring board <b>602</b>, so that the component-holding head <b>690</b> necessarily moves in the Y-axis direction, passing the Y-axis position at which the reflecting mirror <b>796</b> is disposed between the component supply position and the component-mounting position, irrespective of the X-axis positions of the component supply position at the component supply device <b>610</b> and the component-mounting position on the printed-wiring board <b>602</b>. Accordingly, an image of the electronic component <b>606</b> held by the component-holding head <b>690</b> can be taken by the component camera <b>792</b>. The position at which the component-holding head <b>690</b> is located right above the reflecting mirror <b>796</b> and at which the image of the electronic component <b>606</b> is taken by the component camera <b>792</b> is referred to as “component-attitude detecting position” or “component imaging position”.

Where the component-receiving angular position of the electronic component <b>606</b> when the suction nozzle <b>744</b> receives from the component supply device <b>710</b> is different from the component-mounting angular position when the electronic component <b>606</b> is transferred from the suction nozzle <b>744</b> onto the printed-wiring board <b>602</b>, the component-holding head <b>690</b> is rotated by the rotary drive device <b>736</b> to rotate the electronic component <b>606</b> for thereby establishing the component-mounting angular position while the head <b>690</b> is moved from the component-receiving position to the component-attitude detecting position.

When the component-holding head <b>690</b> reaches the component-attitude detecting position, the image of the electronic component <b>606</b> is taken. Since the strobe lights <b>810</b>, <b>814</b> of the imaging system <b>790</b> are disposed on the X-axis slide <b>696</b>, the image of the electronic component <b>606</b> is taken with the component-holding head <b>690</b> held at a Y-axis position corresponding to the component-attitude detecting position, while the head <b>690</b> is moving in the X-axis direction toward the component-mounting position. Image data representative of the image of the electronic component <b>606</b> are compared with stored image data representative of an image of the electronic component <b>606</b> having a nominal XY position and a nominal component-mounting angular position, to calculate XY positioning errors ΔXE and ΔYE and an angular positioning error Δθ.

On the other hand, an image of the fiducial mark <b>778</b> provided on the printed-wiring board <b>602</b> is taken by the fiducial mark camera <b>780</b>, to calculate XY positioning errors ΔXP and ΔYP of the printed-wiring board <b>602</b>. While the component-holding head <b>690</b> is in the process of movement to the component-mounting position, the movement data of the component-holding head <b>690</b> used to move the electronic component <b>606</b> to the component-mounting position are compensated for the error of the predetermined sucking position of the electronic component <b>606</b> due to the XY positioning errors ΔXE, ΔYE, ΔXP, ΔYP of the electronic component <b>606</b> and board <b>602</b> and due to the adjustment for compensation for the angular positioning errorΔθ of the electronic component <b>606</b>. Further, the component-holding head <b>690</b> is rotated by the rotary drive device <b>736</b> for compensation for the angular positioning error Δθ of the electronic component <b>606</b>, so that the electronic component <b>606</b> can be mounted at the predetermined component-mounting position on the printed-wiring board <b>602</b>, with the predetermined attitude, that is, in the predetermined component-mounting angular position. The component-holding head <b>690</b> is moved to the predetermined component-mounting position, and rotated as needed, with concurrent calculation of the XY positioning errors ΔXE, ΔYE, ΔXP, ΔYP and angular positioning error Δθ, and is lowered onto the printed-wiring board <b>602</b> to mount the electronic component <b>606</b> on the board <b>602</b>. Thus, one cycle of component mounting operation is terminated.

In the present embodiment, the XY movement data for moving the component-holding head <b>690</b> are defined in the XY coordinate system established for the electronic-component mounting system <b>601</b>, and the compensation of the XY movement data for compensation for the XY positioning errors ΔXE, ΔYE, ΔXP, ΔYP and the adjustment of the angular position of the component-holding head <b>690</b> for compensation for the angular positioning error Δθ are affected while taking into account the reversal of the image of the electronic component <b>606</b> taken by the component camera <b>792</b> in the upward direction, for instance, the reversal of the image in the Y-axis direction, as in the first embodiment.

The present electronic-component mounting system <b>601</b> has a predetermined component-sucking position on which the XY movement data of the component-holding head <b>690</b> are prepared. In the present embodiment, the zero point of the XY positioning device <b>726</b> is set with respect to the position of the axis of rotation of the component-holding head <b>690</b>. To this end, the position of the rotation axis of the head <b>690</b> is detected to detect a positioning error of the sucking surface <b>772</b>, a positioning error of the component camera <b>792</b> and a positioning error of the tape feeder <b>660</b>, and the XY movement data of the head <b>690</b> are compensated for the detected positioning errors.

The position of the rotation axis of the component-holding head <b>690</b> is detected in the same manner as that of the suction nozzle <b>190</b> in the first embodiment. That is, two images of the sucking surface <b>772</b> of the suction nozzle <b>744</b> placed in respective two angular positions are taken by the component camera <b>792</b> when the component-holding head <b>690</b> is located at the component-attitude detecting position. The images of the sucking surface <b>772</b> are taken in the axial direction of the head <b>690</b> toward the sucking surface <b>772</b>. The position (as represented by the XY coordinate values) of the rotation axis of the head <b>690</b> is obtained on the basis of image data representative of the two images of the sucking surface <b>772</b> in the respective two angular positions, which consist of a predetermined component-receiving angular position to be established when the electronic component <b>606</b> is sucked by the sucking surface <b>772</b>, and another angular position which is spaced 180° from the component-receiving angular position in the circumferential direction of the head <b>690</b>. The XY positioning error of the sucking surface <b>772</b> is detected on the basis of the image data representative of the image taken at the component-receiving angular position.

The XY positions and angular positions of the component cameras <b>792</b> of the two image-taking devices <b>790</b> can be adjusted by a position adjusting device (not shown), for compensation for XY positioning errors and angular positioning errors. The imaging area of each component camera <b>792</b> is defined by the X and Y axes of the XY coordinate system set for the electronic-component mounting system <b>601</b>. The XY positioning errors of the component camera <b>792</b> are deviations of the actual position of the component camera <b>792</b> from the nominal position in the X-axis and Y-axis directions. After the position of the rotation axis of the component-holding head <b>690</b> is detected on the basis of the images of the sucking surface <b>772</b>, the XY positioning errors of the center of the imaging area <b>38</b>B of the component camera <b>792</b> with respect to the rotation axis of the head <b>690</b> are detected to adjust the position of the component camera <b>792</b> in the X-axis and Y-axis directions for compensation for the XY positioning errors. To adjust the angular position of the component camera <b>792</b> for compensation for the angular positioning error, an adjusting jig having mutually perpendicular two reference side surfaces is mounted on the component-holding head <b>690</b>, in place of the suction nozzle <b>744</b>, such that the side surfaces are parallel to the rotation axis of the head <b>690</b> and such that the adjusting jig is rotatable about its axis relative to the head <b>690</b>. The adjusting jig is rotated about its axis to an angular position in which the two side surfaces of the adjusting jig are parallel to the X-axis and Y-axis directions, respectively. To confirm the parallelism of the side surfaces to the X-axis and Y-axis directions, a dial indicator is fixed on a suitable stationary member such that the plunger of the dial indicator is held in contact with one of the two side surfaces of the adjusting jig. The parallelism can be confirmed by reading the dial indicator while the head <b>690</b> is moved in the X-axis or Y-axis direction by the XY positioning device <b>726</b>. If the reading of the dial indicator whose plunger is held in contact with one of the two side surfaces remains constant when the head <b>690</b> is moved in the Y-axis direction, for instance, this means that the above-indicated one side surface is parallel to the Y-axis direction. The dial indicator may be removably fixed on the PWB support device <b>616</b>. After the angular position of the adjusting jig is adjusted such that the two side surfaces of the adjusting jig are parallel to the respective X-axis and Y-axis directions, an image of the adjusting jig is taken by the component camera <b>792</b>, and the angular position of the component camera <b>792</b> is adjusted on the basis of image data representative of the image of the adjusting jig. The adjustment of the angular position of the component camera <b>792</b> is made while the mounting system <b>609</b> is not in the component mounting operation, as in the first embodiment.

In the present embodiment, the component mounting device <b>608</b> has only one suction nozzle <b>744</b>, and the axis of rotation of the suction nozzle <b>744</b> is the same as the axis of rotation of the component-holding head <b>690</b>, namely, there is not an error of the rotation axis of the head <b>690</b>, so that the XY movement data of the head <b>690</b> are adjusted for compensation for the positioning error of the sucking surface <b>772</b>. Further, the XY positioning error of the tape feeder <b>660</b> is detected after initiation of the component mounting operation, on the basis of the XY positioning error of the electronic component <b>606</b>, and the XY movement data are adjusted for compensation for the XY positioning error of the tape feeder <b>660</b>. The positioning error of the rotation axis of the head <b>690</b>, if any, is eliminated by adjusting the XY movement data for compensation for the positioning error of the tape feeder <b>660</b>. These adjustments are also made while taking into account the reversal of the images taken by the component camera <b>792</b> in the upward direction.

In the present embodiment, the component supply devices <b>610</b>, <b>612</b> are stationary while the component-holding head <b>690</b> is movable in the X-axis and Y-axis directions by the XY positioning device <b>726</b>. Accordingly, the positioning errors in the X-axis and Y-axis directions can be eliminated by adjusting the XY movement data of the component-holding head <b>690</b>. Therefore, the sucking position of the electronic component <b>606</b> is set in both of the X-axis and Y-axis directions, and the positioning errors of the sucking surface <b>772</b> and the tape feeder <b>660</b> are obtained in the X-axis and Y-axis directions. The XY movement data of the head <b>690</b> are prepared and adjusted in the X-axis and Y-axis directions so that the center <b>201</b>A of the sucking surface <b>772</b> is aligned with the predetermined sucking position <b>38</b>A of the electronic component <b>38</b>, whereby the electronic component <b>38</b> can be sucked at its predetermined sucking position <b>38</b>A of the sucking surface <b>772</b>.

When a predetermined detecting condition is satisfied after the component mounting operation is initiated, the position of the rotation axis of the head <b>690</b> and the positioning errors of the sucking surface <b>772</b> are detected. Two images of the sucking surface <b>772</b> are taken by the component camera <b>792</b> with the head <b>690</b> placed in respective two angular positions, in the same manner as used to take the two images before the component mounting operation, and the rotation axis of the head <b>690</b> is detected on the basis of the two images, and the positioning errors of the sucking surface <b>772</b> with respect to the rotation axis are detected to adjust the XY movement data. During the component mounting operation, the XY and angular positions of the component camera <b>792</b> are not adjusted, but the center position error of the imaging area of the component camera <b>792</b> with respect to the rotation axis of the head <b>690</b> is adjusted by calculation. Described in detail, the position of the rotation axis of the head <b>690</b> is obtained on the basis of the center position error of the imaging area with respect to the rotation axis of the head <b>690</b>, and the XY positioning error of the electronic component <b>606</b> with respect to the obtained position of the rotation axis is detected. Further, an error of the sucking position <b>38</b>A of the electronic component <b>38</b> due to the adjustment of the angular position of the electronic component <b>606</b> for compensation of the angular positioning error is obtained.

Where a plurality of component mounting units <b>738</b> are provided, a plurality of component-holding heads <b>690</b> are provided. In this case, a selected one of the plurality of heads <b>690</b> is used as a reference head whose rotation axis is used as a reference rotation axis, and the XY positioning errors of the rotation axis of the other heads <b>690</b> are detected with respect to the reference rotation axis. The component-holding head <b>690</b> may be modified to hold a plurality of suction nozzles <b>744</b>. In this case, a selected one of the suction nozzles <b>744</b> is used as a reference suction nozzle.

Where the positioning errors of the sucking surface of the suction nozzle and other positioning errors are detected while the mounting system <b>601</b> is not in the component mounting operation, the positioning errors of the image-taking devices may be corrected by adjusting the center position of the electronic component, without adjusting the actual positions of the image-taking devices. In this case, the position adjustment of the image-taking devices is affected only when the positioning errors such as those of the sucking surface of the suction nozzle are detected during manufacture or maintenance inspection of the mounting system <b>601</b>. That is, the positions of the image-taking devices are not adjusted even if the positioning errors of the image-taking devices are detected upon detection of the positioning errors of the sucking surface and other positioning errors prior to a component mounting operation. The detected positioning errors of the mage-taking devices are corrected by adjusting the center position of the electronic component. In this case, the horizontal positioning error of the electronic component with respect to the detected rotation axis of the reference suction nozzle is detected, and the positions of the rotation axes of the other suction nozzles are obtained on the basis of the position of the rotation axis of the reference suction nozzle and the positioning error of the image-taking device with respect to the rotation axis of the reference suction nozzle, so that the errors of the sucking position of the electronic component with respect to the rotation axes of the other suction nozzles are detected.

In the illustrated embodiments described above, the image of the sucking surface of the suction nozzle is taken by the component camera of image-taking device provided to take the image of the electronic component held by the suction nozzle. However, the image of the sucking surface may be taken by another image-taking device.

In the electronic component mounting system according to the first embodiment of FIGS. 1-14 using the two component cameras <b>350</b>, <b>352</b>, only one component camera may be provided. In this instance, the component camera may be arranged to adjust its ratio of magnification.

While the presently preferred embodiments of the present invention have been described in detail, for illustrative purpose only, it is to be understood that the present invention may be embodied with various changes and improvements, such as those described in the SUMMARY OF THE INVENTION, which may occur to those skilled in the art.